KVM: selftests: Drop unnecessary rule for STATIC_LIBS

Drop the "all: $(STATIC_LIBS)" rule. The KVM selftests already depend
on $(STATIC_LIBS), so there is no reason to have an extra "all" rule.

Suggested-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220520233249.3776001-8-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>