Unpinning tab intermittently does not display the title on tabs

[bbondy]

Fix #9608

Auditors: @cezaraugusto

Note that since it's intermittent I think the test would also pass before, but I can't find a way to get a unique test to always fail. Same as if I test manually

The test will at least ensure that unpinning gives a title always
though.

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.

Reviewer Checklist:

Tests

• Adequate test coverage exists to prevent regressions
• Tests should be independent and work correctly when run individually or as a suite ref
• New files have MPL2 license header

[cezaraugusto]

LGTM

[bbondy]

A+++++++ on the test! Would review again!!!