simpleperf: ProtoFileReportLib: remove trace-offcpu mode check

On old Android versions (<= S), a profile may be generated
by simpleperf before aosp/1897156. It can't pass the check,
but actually is still reportable.

Bug: 325484390
Test: run test.py -p TestProtoFileReportLib*
Test: run report_html.py manually
Change-Id: Ide0e844fb835c98b06e773fc362be39e3b6cb142
1 file changed