[NFC][XCOFF] Use yaml2obj in llvm-objdump/XCOFF/section-headers.test instead of binary files.

Summary: This a minor patch to refactor the test file,
llvm-objdump/XCOFF/section-headers.test, to use yaml2obj
for this testing rather than a canned binary.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D103146