TestUpgradeInfoURLs only works for some architectures

[Millak]

Based on the way the test is written, it can only pass on a matrix of OSes (mac, windows, linux) by architectures (386, amd64, arm64). Any architecture (or OS) which falls outside of this matrix will automatically fail the test. Adding a fallback of

default:
    archType = runtime.GOARCH

will allow the test to pass on, say, riscv64, but it seems like a hack, especially if there isn't going to be a release binary pre-built for that architecture. Ideally the test would be limited to the architecture/OS combinations which either may pass or which would actually exist.

[apteryks]

I haven't looked, but this being Go, I don't think there's any valid reason tests should target specific architectures. Perhaps this can be simplified out.