fix(config): Use boolean in `codecov.yml` (#51699)

This switches from using `yes` to using `true` in `codecov.yml`, as specified in the schema for the file[1], so our linter will stop yelling at us. (This also matches the example in the codecov docs[2].)

[1] https://json.schemastore.org/codecov.json
[2] https://docs.codecov.com/docs/pull-request-comments#configuration

codecov.yml

@@ -72,5 +72,5 @@ comment:
   # already exists, and a newer commit results in no coverage change for the
   # entire pull, the comment will be deleted.
   require_changes: true
-  require_base: yes # must have a base report to post
-  require_head: yes # must have a head report to post
+  require_base: true # must have a base report to post
+  require_head: true # must have a head report to post