CONTRIBUTING.md: Use a proper example for stewardship label

The bug guidelines example of what should be marked with the stewardship
label goes against the principles of GitLab as stated in
https://about.gitlab.com/stewardship/ since mentions removing a feature
from GitLab CE to make it exclusive of GitLab EE.

The example should be the opposite, where GitLab Inc. is bringing a
feature from GitLab EE to GitLab CE.

This commit changes the example to reflect this situation.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/43579

CONTRIBUTING.md

@@ -397,9 +397,9 @@ For issues related to the open source stewardship of GitLab,
 there is the ~"stewardship" label.
 
 This label is to be used for issues in which the stewardship of GitLab
-is a topic of discussion. For instance if GitLab Inc. is planning to remove
-features from GitLab CE to make exclusive in GitLab EE, related issues
-would be labelled with ~"stewardship".
+is a topic of discussion. For instance if GitLab Inc. is planning to add
+features from GitLab EE to GitLab CE, related issues would be labelled with
+~"stewardship".
 
 A recent example of this was the issue for
 [bringing the time tracking API to GitLab CE][time-tracking-issue].