checkdocs: trim links off docs/ markdowns before spellcheck

So that we can use words in links without having them spellchecked.

Closes #15910

.github/workflows/checkdocs.yml

@@ -120,6 +120,9 @@ jobs:
       - name: trim cmdline docs markdown _*.md files
         run: find docs/cmdline-opts -name "_*.md" -print0 | xargs -0 -n1 .github/scripts/cleancmd.pl --no-header
 
+      - name: trim docs/ markdown _*.md files
+        run: git ls-files docs/*.md docs/internals/*.md | xargs -n1 .github/scripts/cleancmd.pl --no-header
+
       - name: setup the custom wordlist
         run: grep -v '^#' .github/scripts/spellcheck.words >  wordlist.txt