circleci: remove gopath

[alebcay]

• Have you followed the guidelines for contributing?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with brew install --build-from-source <formula>, where <formula> is the name of the formula you're submitting?
• Is your test running fine brew test <formula>, where <formula> is the name of the formula you're submitting?
• Does your build pass brew audit --strict <formula> (after doing brew install <formula>)?

---

Remove GOPATH as formula supports Go modules.

Relates to #47627.

[alebcay]

==> brew test circleci --verbose
==> FAILED
Testing circleci
/usr/bin/sandbox-exec -f /private/tmp/homebrew20191210-19705-ttsrzo.sb ruby -W0 -I $LOAD_PATH -- /usr/local/Homebrew/Library/Homebrew/test.rb /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/circleci.rb --verbose
==> /usr/local/Cellar/circleci/0.1.5879/bin/circleci version
panic: stat /private/tmp/_data/data.yml: no such file or directory

goroutine 1 [running]:
github.com/CircleCI-Public/circleci-cli/cmd.MakeCommands(0xc000094058)
	github.com/CircleCI-Public/circleci-cli@/cmd/root.go:88 +0xe2e
github.com/CircleCI-Public/circleci-cli/cmd.Execute()
	github.com/CircleCI-Public/circleci-cli@/cmd/root.go:36 +0x22
main.main()
	github.com/CircleCI-Public/circleci-cli@/main.go:9 +0x20
Error: circleci: failed
An exception occurred within a child process:
  Test::Unit::AssertionFailedError: <0> expected but was
<2>.

Reproduced issue locally. Attempted removing the added -trimpath but issue persisted, so the error is arising from the actual removal of GOPATH, not just the change in flags.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.