Dangerfile: Add group::gitaly::git and group::gitaly::cluster
These two new groups are going to replace gitaly::git and gitaly::cluster. See gitlab-com/www-gitlab-com!122793 (merged) for details. Add them to the INHERITABLE_LABELS so they get inherited from issues.
Also the group::gitaly label can also be inherited, in the situation that the issue is a group::gitaly issue but a community contributor or someone on another team ends up contributing to it.