cookies: remove unused header

Commit 1c1d9f1aff removed the last use
for the inet_pton.h headerfile, this removes the inclusion of the
header.

Closes: #7182
Reviewed-by: Daniel Stenberg <daniel@haxx.se>

lib/cookie.c

@@ -95,7 +95,6 @@ Example set of cookies:
 #include "strcase.h"
 #include "curl_get_line.h"
 #include "curl_memrchr.h"
-#include "inet_pton.h"
 #include "parsedate.h"
 #include "rand.h"
 #include "rename.h"