Disable nullability checks for overrides of generics am: 48cdc3f1c7 am: 3fabaaf42c am: f61c0b3529

Original change: https://android-review.googlesource.com/c/platform/tools/metalava/+/2009515

Change-Id: I0d842b74a469cb8808f0a0889ad94fc5818fd704