cmd/go: set GO111MODULE=off explicitly in TestScript/list_test_err
cmd/go: set GO111MODULE=off explicitly in TestScript/list_test_err

This test was added after CL 162697.

Updates #30228

Change-Id: Ia33ad3adc99e53b0b03e68906dc1f2e39234e2cf
Reviewed-on: https://go-review.googlesource.com/c/go/+/166697
Run-TryBot: Bryan C. Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/go,nawawi/go,josharian/go,cloudflare/go,golang/go,akutz/go,CAFxX/go,cloudflare/go,josharian/go,CAFxX/go,nawawi/go,nawawi/go,golang/go,golang/go,akutz/go,akutz/go,josharian/go,CAFxX/go,nawawi/go,nawawi/go,cloudflare/go,nawawi/go,josharian/go,cloudflare/go,golang/go,CAFxX/go,golang/go,josharian/go,josharian/go,josharian/go,golang/go,akutz/go,cloudflare/go,cloudflare/go,CAFxX/go,akutz/go,golang/go,josharian/go,CAFxX/go,CAFxX/go,akutz/go,nawawi/go,akutz/go,cloudflare/go,CAFxX/go,cloudflare/go,akutz/go,nawawi/go