KVM: selftests: Drop the return of remove_event()

None of the callers consume remove_event(), and it incorrectly implies
that the incoming filter isn't modified. Drop the return.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
Link: https://lore.kernel.org/r/20230810090945.16053-3-cloudliang@tencent.com


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