Remove CPU tracepoint test from GPU work test class

testReadTracingEvents test checks the CPU frequency tracepoint to
make sure the tracepoint system is available and functional, but
it's not useful to do this check within the GPU work related class.

Bug: 356851636
Flag: EXEMPT test
Test: GpuWorkTracepointTest#testReadTracingEvents
Change-Id: I672c14b761687912456941db441915414bfb4bca