Intermittent `403 Forbidden` error in the `Build ruby.wasm` Github Actions workflow

[mashallah]

The docker/build-push-action step intermittently fails during the build-builder-image job. I had the same problem recently and would like to offer a PR with the updates that worked for us.

Examples

• https://github.com/ruby/ruby.wasm/actions/runs/10484098839/job/29037840314#step:6:273

 > exporting to image:
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ERROR: failed to solve: failed to push ghcr.io/ruby/ruby.wasm/builder/wasm32-unknown-wasip1:main: unexpected status from POST request to https://ghcr.io/v2/ruby/ruby.wasm/builder/wasm32-unknown-wasip1/blobs/uploads/: 403 Forbidden
Error: buildx failed with: ERROR: failed to solve: failed to push ghcr.io/ruby/ruby.wasm/builder/wasm32-unknown-wasip1:main: unexpected status from POST request to https://ghcr.io/v2/ruby/ruby.wasm/builder/wasm32-unknown-wasip1/blobs/uploads/: 403 Forbidden