Remove unnecessary project instance variable

- no longer needed.
- tracked this back to https://gitlab.com/gitlab-org/gitlab/-/commit/aaa1c94239df831d10489d686d8883b49d601f43
   where 'people/members' were attached to a project
- no longer needed as @project isn't referenced

app/controllers/groups/group_members_controller.rb

@@ -24,8 +24,6 @@ class Groups::GroupMembersController < Groups::ApplicationController
   def index
     @sort = params[:sort].presence || sort_value_name
 
-    @project = @group.projects.find(params[:project_id]) if params[:project_id]
-
     @members = GroupMembersFinder
       .new(@group, current_user, params: filter_params)
       .execute(include_relations: requested_relations)