Task: async tests should not call test.end() after upgrading to Tape v5

After Twing updates to Tape v5 (from v4)…

According to the Tape docs:

Do not call t.end() if your test callback returns a Promise.

There are 28 tests that use an async function that returns a Promise; they all use t.end() in them, but those calls should be removed when Tape is upgraded to v5.