Clean up page custom urls

[andreiio]

Once #4870 is fixed upstream, url should be dropped from pages' front-matter and replaced with the commented out slug in the following files:

• content/about/index.en.md
• content/about/index.ro.md
• content/code-of-conduct/index.en.md
• content/code-of-conduct/index.ro.md
• content/community/index.en.md
• content/community/index.ro.md
• content/donate/error/index.en.md
• content/donate/error/index.ro.md
• content/donate/index.en.md
• content/donate/index.ro.md
• content/donate/success/index.en.md
• content/donate/success/index.ro.md
• content/get-involved/index.en.md
• content/get-involved/index.ro.md
• content/partners/index.en.md
• content/partners/index.ro.md
• content/supporters/index.en.md
• content/supporters/index.ro.md

 ---
 title: Community
-# slug: community
-url: /en/community/
+slug: community