Changed to print the directory name according to the l10n language. (#18473)

When a localization user uses diff_l10n_branches.py,
the directory of content on 'Proposed Solution' is fixed.
Thus, this commit changes the directory name according to the l10n language.

Author: claudiajkang

scripts/diff_l10n_branches.py

@@ -39,7 +39,7 @@
 ...
 # check what is updated in the upstream 
 git diff {{ l_commit }} {{ r_commit }} -- {{ files_to_be_modified.0.filepath }}
-# apply changes to content/ko
+# apply changes to {{ l10n_lang_path }}
 vi {{ files_to_be_modified.0.filepath | replace(src_lang_path, l10n_lang_path) }}
 ...
 # commit and push