docs: clarify data replacement policy for MIME API

The API documentation for the MIME functions specify that the parts
can be set twice, with the last call winning.  While true, the user
can set the parts n times for n > 2, reword to specify multiple API
calls instead.

Closes: #8860
Reviewed-by: Daniel Stenberg <daniel@haxx.se>

docs/libcurl/curl_mime_data.3

@@ -39,8 +39,8 @@ storage may safely be reused after call.
 character string.
 \fIpart\fP is the part's to assign contents to.
 
-Setting a part's contents twice is valid: only the value set by the last call
-is retained. It is possible to unassign part's contents by setting
+Setting a part's contents multiple times is valid: only the value set by the
+last call is retained. It is possible to unassign part's contents by setting
 \fIdata\fP to NULL.
 
 Setting large data is memory consuming: one might consider using

docs/libcurl/curl_mime_encoder.3

@@ -37,8 +37,8 @@ transmitted.
 set to NULL to disable an encoder previously attached to the part. The encoding
 scheme storage may safely be reused after this function returns.
 
-Setting a part's encoder twice is valid: only the value set by the last call is
-retained.
+Setting a part's encoder multiple times is valid: only the value set by the
+last call is retained.
 
 Upon multipart rendering, the part's content is encoded according to the
 pertaining scheme and a corresponding \fI"Content-Transfer-Encoding"\fP header

docs/libcurl/curl_mime_filedata.3

@@ -52,8 +52,8 @@ If the file size cannot be determined before actually reading it (such as for
 a device or named pipe), the whole mime structure containing the part
 will be transferred as chunks by HTTP and rejected by IMAP.
 
-Setting a part's contents twice is valid: only the value set by the last call
-is retained.
+Setting a part's contents multiple times is valid: only the value set by the
+last call is retained.
 .SH EXAMPLE
 .nf
  curl_mime *mime;

docs/libcurl/curl_mime_filename.3

@@ -42,7 +42,7 @@ to NULL to remove a previously attached remote file name.
 
 The remote file name string is copied into the part, thus the associated
 storage may safely be released or reused after call. Setting a part's file
-name twice is valid: only the value set by the last call is retained.
+name multiple times is valid: only the value set by the last call is retained.
 .SH EXAMPLE
 .nf
  curl_mime *mime;

docs/libcurl/curl_mime_headers.3

@@ -41,8 +41,8 @@ to remove a previously attached custom header list.
 replacement or mime structure deletion; in this case the list must not be
 freed explicitly.
 
-Setting a part's custom headers list twice is valid: only the value set by
-the last call is retained.
+Setting a part's custom headers list multiple times is valid: only the value
+set by the last call is retained.
 .SH EXAMPLE
 .nf
  struct curl_slist *headers = NULL;

docs/libcurl/curl_mime_name.3

@@ -37,9 +37,9 @@ fields are named.
 \fIname\fP points to the null-terminated name string.
 
 The name string is copied into the part, thus the associated storage may
-safely be released or reused after call. Setting a part's name twice is valid:
-only the value set by the last call is retained. It is possible to "unname" a
-part by setting \fIname\fP to NULL.
+safely be released or reused after call. Setting a part's name multiple times
+is valid: only the value set by the last call is retained. It is possible to
+"unname" a part by setting \fIname\fP to NULL.
 .SH EXAMPLE
 .nf
  curl_mime *mime;

docs/libcurl/curl_mime_subparts.3

@@ -39,9 +39,9 @@ structure.
 multipart part and must not be freed explicitly. It may however be updated by
 subsequent calls to mime API functions.
 
-Setting a part's contents twice is valid: only the value set by the last call
-is retained. It is possible to unassign previous part's contents by setting
-\fIsubparts\fP to NULL.
+Setting a part's contents multiple times is valid: only the value set by the
+last call is retained. It is possible to unassign previous part's contents by
+setting \fIsubparts\fP to NULL.
 .SH EXAMPLE
 .nf
  /* The inline part is an alternative proposing the html and the text

docs/libcurl/curl_mime_type.3

@@ -37,8 +37,8 @@ CURLcode curl_mime_type(curl_mimepart *part, const char *mimetype);
 set to NULL to remove a previously attached mime type.
 
 The mime type string is copied into the part, thus the associated storage may
-safely be released or reused after call. Setting a part's type twice is valid:
-only the value set by the last call is retained.
+safely be released or reused after call. Setting a part's type multiple times
+is valid: only the value set by the last call is retained.
 
 In the absence of a mime type and if needed by the protocol specifications,
 a default mime type is determined by the context: