[5.0.x] Corrected note about using accents in writing documentation contributing guide.

Backport of 16115771020eaededb56fdfbcfec978e950b6a9a from main

docs/internals/contributing/writing-documentation.txt

@@ -543,7 +543,8 @@ file and line number where they occur will be saved to
 If you encounter false-positives (error output that actually is correct), do
 one of the following:
 
-* Surround inline code or brand/technology names with grave accents (`).
+* Surround inline code or brand/technology names with double grave accents
+  (``).
 * Find synonyms that the spell checker recognizes.
 * If, and only if, you are sure the word you are using is correct - add it
   to ``docs/spelling_wordlist`` (please keep the list in alphabetical order).