Use backticks to format file name in using-submodules-with-github-pag…

…es.md (#35838)

Signed-off-by: Paulina Kalicka <71526180+paulinek13@users.noreply.github.com>
Co-authored-by: Alex Nguyen <150945400+nguyenalex836@users.noreply.github.com>

content/pages/getting-started-with-github-pages/using-submodules-with-github-pages.md

@@ -18,7 +18,7 @@ If the repository for your {% data variables.product.prodname_pages %} site cont
 
 You can only use submodules that point to public repositories, because the {% data variables.product.prodname_pages %} server cannot access private repositories.
 
-Use the `https://` read-only URL for your submodules, including nested submodules. You can make this change in your _.gitmodules_ file.
+Use the `https://` read-only URL for your submodules, including nested submodules. You can make this change in your `.gitmodules` file.
 
 ## Further reading