gracedb-2.21.3

This contains fixes to minor visual bugs and broken links that revealed themselves in the last week of ER-15:

• adding far back to public superevent info table that was inexplicably removed after O3
• "O3" replaced with "O4" on pipeline management page
• change er15+ circular links to point to gcn query page: 035a70a9, 1c3b51c8