x/build: new luci choose tryjobs is not accessible even tho I have permissions for the gerrit one

[Jorropo]

In gerrit trying to use the new CHOOSE TRYJOBS tab for luci:

I get this error in the console:

Failed to schedule builds: Error: "user:jorropo.pgm@gmail.com" does not have permission "buildbucket.builds.add" in bucket "golang/try"

Even tho I was able to do it through the voting system: https://go-review.googlesource.com/c/go/+/495115/comments/e46ce1cd_fd4e7fe9

[heschi]

Thanks. We should probably grant that permission to everyone with may-start-trybots, but we haven't fully understood the implications yet.

cc @golang/release