Update screenshots in tutorial for PR mergers #11
Description
The screenshots in https://jtr13.github.io/cc21fall2/tutorial-for-pull-request-mergers.html should be updated for a number of reasons:
- some show "merged" before the PR was actually merged
- master is now main
- translations are no longer accepted for the community contribution
- there may have been small changes to the GitHub interface since the screenshots were taken