Remove upx from build

[jkutner]

The upx package is no longer available for debian and newer versions of the golang base image. Because upx has caused us some issues locally with Crowdstrike, we are removing it from the build process.

This increases the size of the github-actions images by about 3MB each

[edmorley]

This increases the size of the github-actions images by about 3MB each

I think that must be the uncompressed image size, since the layer metadata for the binary's layer reports the gzipped size as only increasing from 2,165,499 to 2,368,134 bytes:
https://github.com/orgs/buildpacks/packages/container/actions%2Fregistry%2Frequest-add-entry/92224166?tag=5.2.0
https://github.com/orgs/buildpacks/packages/container/actions%2Fregistry%2Frequest-add-entry/115507685?tag=5.3.1
(the manifest is shown at the bottom of each of those pages)

As such the bytes over the wire barely changed (which for CI use-cases is more important than bytes on disk) - further validating the decision to simplify things here and remove UPX :-)