Remove just-added tests for to_timestamp(float8) with out-of-range inputs.

Remove just-added tests for to_timestamp(float8) with out-of-range inputs.

Reporting the specific out-of-range input value produces platform-dependent
results.  We could skip reporting the value, but that's contrary to our
message style guidelines and unhelpful to users.  Or we could add a
separate expected-output file for Windows, but that would be a substantial
maintenance burden, and these test cases seem unlikely to be worth it.

Per buildfarm.