[build] Gradle build: sharing build outputs uploads about 1GB

[lhotari]

It looks like it's uploading unnecessary files:
https://github.com/apache/pulsar/actions/runs/23648737440/job/68887602878?pr=25409#step:11:156

Uploaded bytes 1005168785
Finished uploading artifact content to blob storage!
SHA256 digest of uploaded artifact zip is 5ed5ef3017aeb99aebdaebafacaac81ce800339ec5659b42eab3e4c0ef558547
Finalizing artifact upload
Artifact gradle-build-outputs.zip successfully finalized. Artifact ID 6144784161
Artifact gradle-build-outputs has been successfully uploaded! Final size is 1005168785 bytes. Artifact ID is 6144784161
Artifact download URL: https://github.com/apache/pulsar/actions/runs/23648737440/artifacts/6144784161

@merlimat Can we make this more efficient?