cmd/gopherbot: update link to troubleshooting page
cmd/gopherbot: update link to troubleshooting page

We're moving off of the Wiki and to committed markdown.

Change-Id: I931064bf42cc52d76f2044475a3c1df3edefc71e
Reviewed-on: https://go-review.googlesource.com/c/build/+/196697
Run-TryBot: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>

golang/build,golang/build,golang/build,golang/build