Remove redundant test name prefixes now that test names are fully qualified

Follow up to #19079, which made test names fully qualified.

This fixes tests that now-redundant information in their test names. For example here's a fully qualified test name before the changes in this commit:

"priority_queue.test.std.PriorityQueue: shrinkAndFree"

and the same test's name after the changes in this commit:

"priority_queue.test.shrinkAndFree"