cmd/gopherbot: remove automated milestone settings for pkgsite
cmd/gopherbot: remove automated milestone settings for pkgsite

The tools team plans to manually triage pkgsite
issues and the pkgsite milestones for license
and search will no longer exist.

Change-Id: I476bfb6544645be89d78d25b0dee6a9634b3dba7
Reviewed-on: https://go-review.googlesource.com/c/build/+/407499
Run-TryBot: Jamal Carvalho <e0195770807aa8c82b0b128d9c0423b5ad035172@golang.org>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Alex Rakoczy <60c6d277a8bd81de7fdde19201bf9c58a3df08f4@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <d7e82c3c07f92613bcbf9a1e88f6b96c13caa3b0@gmail.com>

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