fix markdownlint

Signed-off-by: Xinyu Zhou <[email protected]>

Author: Xinyu Zhou

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -1233,4 +1233,4 @@ PROXY_HOSTS = *.github.com
 - `SHOW_FOOTER_BRANDING`: **false**: Show Gitea branding in the footer.
 - `SHOW_FOOTER_VERSION`: **true**: Show Gitea and Go version information in the footer.
 - `SHOW_FOOTER_TEMPLATE_LOAD_TIME`: **true**: Show time of template execution in the footer.
-- `ENABLE_SITEMAP`: **true**: Generate sitemap.
+- `ENABLE_SITEMAP`: **true**: Generate sitemap.