Decide what to do with GOPATH builds/tests

[tonyo]

At the moment the GOPATH build fails because opentelemetry-go dep now has 1.19+ symbols (atomic.Bool, atomic.Pointer) in their main branch.

Example https://github.com/getsentry/sentry-go/actions/runs/4563862504/jobs/8052889793

Building otel module in that test has been removed here, but we should consider dumping that test altogether, given the fact that it's 2023, and Go modules have been the thing for a long time already.