KVM: selftests: Drop now-redundant checks on PERF_CAPABILITIES writes

Now that vcpu_set_msr() verifies the expected "read what was wrote"
semantics of all durable MSRs, including PERF_CAPABILITIES, drop the
now-redundant manual checks in the VMX PMU caps test.

Link: https://lore.kernel.org/r/20230311004618.920745-14-seanjc@google.com


Signed-off-by: Sean Christopherson <seanjc@google.com>