Temporal: Remove string parsing tests from staging

I've replaced these string parsing tests with more thorough snapshotting
tests in proposal-temporal:
tc39/proposal-temporal#3286

I'll run those against each implementation to find out any remaining
implementation divergences, and add more targeted tests to test262
covering any that I find. But for the time being, it doesn't make sense
to keep these here.

Supersedes tc39#4286.

Author: ptomato