Merge pull request matplotlib#19799 from meeseeksmachine/auto-backport-of-pr-19786-on-v3.4.0-doc

Backport PR matplotlib#19786 on branch v3.4.0-doc (Fix code-of-conduct link on doc homepage.)

Author: timhoffm

doc/index.rst

@@ -78,7 +78,8 @@ Join our community!
 ~~~~~~~~~~~~~~~~~~~
 
 Matplotlib is a welcoming, inclusive project, and everyone within the community
-is expected to abide by our `code of conduct <../CODE_OF_CONDUCT.md>`_.
+is expected to abide by our `code of conduct
+<https://github.com/matplotlib/matplotlib/blob/master/CODE_OF_CONDUCT.md>`_.
 
 
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