plugin: remove unused func
plugin: remove unused func

Change-Id: Ife29464d581f00940af7ef9251bf99661c1350b6
GitHub-Last-Rev: d7747706584b06b619fc78a85b6b9bfe619467c8
GitHub-Pull-Request: golang/go#26740
Reviewed-on: https://go-review.googlesource.com/127195
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

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