test: clean up skipped tests

[kfarnung]

• Fixed a lint issue
• Switch buffer tests from .apply() to .map().join()

Checklist

• [x] make -j4 test (UNIX), or vcbuild test (Windows) passes
• [x] tests and/or benchmarks are included
• [x] documentation is changed or added
• [x] commit message follows commit guidelines

[kfarnung]

CI: https://ci.nodejs.org/job/chakracore-test/394/

[kfarnung]

So far these changes all pass on my Windows and Ubuntu machines. Waiting to see what the CI has to say for further adjustments.