[testing] - integrations/examples/buildx erroring for `Verify examples` tests

Currently there is a `Verify examples` test that runs changes examples when files are changed in integration/examples/*. It seems that currently the `integration/examples/custom-buildx` is broken when run via `Verify examples` but it only run when this example is modified:
```
>> integration/examples/custom-buildx
Generating tags...
- skaffold-examples-buildx -> skaffold-examples-buildx:latest
Starting build...
multi-platform build requires pushing images to a valid container registry. To run multi-platform builds, set --push to true and set a container registry with --default-repo or in the global config.
Error: Process completed with exit code 1.
```

It seems the root cause is that multi-platform builds require pushing an image but the test itself goes through a path that does not push the image: