MM-36909: Skip flaky CreateDefaultMemberships for now (#17925)

```release-note
NONE
```

app/syncables_test.go

@@ -13,6 +13,7 @@ import (
 )
 
 func TestCreateDefaultMemberships(t *testing.T) {
+	t.Skip("MM-36909")
 	th := Setup(t).InitBasic()
 	defer th.TearDown()