cmd/internal/testdir: stop manually adding GOROOT/bin to PATH
The go command already places $GOROOT/bin at the beginning of $PATH in
the test's environment as of Go 1.19¹, so there's no need for the test
to do it anymore. Start enjoying yet another benefit of using 'go test'.
¹ See go.dev/issue/57050.
For #56844.
Change-Id: If7732cd8b8979eabf185485d3c73858a4e546d69
Reviewed-on: https://go-review.googlesource.com/c/go/+/498271 Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>