KVM: selftests: Drop "all done!" printf() from PERF_CAPABILITIES test

Drop the arbitrary "done" message from the VMX PMU caps test, it's pretty
obvious the test is done when the process exits.

Link: https://lore.kernel.org/r/20230311004618.920745-19-seanjc@google.com


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