test: add test of fs.promises write for non-string buffers
- To increase fs promises coverage, add test of fs.promises write for non-string buffers.
- Fix comment of fs.promises write that was "read", despite "write".
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
commit message follows commit guidelines