Re-enable TestMixedBuildUsesStubs

This was disabled because of some non-determinism in Soong, which has
been been fixed in aosp/2559590

Bug: 275313114
Test: go test ./cc -run TestMixedBuildUsesStubs -count 1000
Change-Id: I261dc785c832e66f8e213132c19111b8b90e40e9
diff --git a/cc/cc_test.go b/cc/cc_test.go
index 787669c..a1d6bdc 100644
--- a/cc/cc_test.go
+++ b/cc/cc_test.go
@@ -3683,9 +3683,6 @@
 }
 
 func TestMixedBuildUsesStubs(t *testing.T) {
-	// TODO(b/275313114): Test exposes non-determinism which should be corrected and the test
-	// reenabled.
-	t.Skip()
 	t.Parallel()
 	bp := `
 		cc_library_shared {