translation: mark vim.pot as linguist-generated, ignore msg locations in vim.pot

Update the textconv filter to filter out changes in the comments
pointing to the location of the message.

Also remove the comments in vim.pot that mention the message location.
Since those will be ignored using vims textconv filter, it does not make
sense to keep them, they would get out of sync anyhow.

closes: #17782

Co-authored-by: Illia Bobyr <illia.bobyr@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

.gitattributes

@@ -3,7 +3,15 @@ src/testdir/test42.in diff
 # vim.pot may change just by incrementing a patch number
 # so ignore the following differences:
 # - POT-Creation Date
-# - comments in version.c for line numbers:
+# - comments pointing to the message source location in
+#   *.c/*.h/*.vim/*.cpp/*.in/*.xs files followed by line numbers
 # set this up using:
-# git config diff.ignore_pot_date.textconv 'grep -Ev "^.(POT-Creation-Date:|.*version\.c).*"'
-src/po/vim.pot diff=ignore_pot_date
+# git config diff.ignore_vim_pot.textconv "grep -Ev '^.(POT-Creation-Date:|.*\\.([ch]|vim|in|xs|cpp):).*$'"
+src/po/vim.pot diff=ignore_vim_pot
+
+# GitHub reacts to the `linguist-generated` attribute, by ignoring marked files
+# for the repository's language statistics and hiddning changes in these files
+# by default in diffs.
+#
+# https://docs.github.com/en/repositories/working-with-files/managing-files/customizing-how-changed-files-appear-on-github
+src/po/vim.pot linguist-generated=true