Fit GitAccess specs

These specs never ran due to incorrect indentation: the `context` blocks
were inside the `before`.

spec/lib/gitlab/git_access_spec.rb

@@ -215,7 +215,9 @@ describe Gitlab::GitAccess, lib: true do
 
     def stub_git_hooks
       # Running the `pre-receive` hook is expensive, and not necessary for this test.
-      allow_any_instance_of(GitHooksService).to receive(:execute).and_yield(GitHooksService.new)
+      allow_any_instance_of(GitHooksService).to receive(:execute) do |service, &block|
+        block.call(service)
+      end
     end
 
     def merge_into_protected_branch
@@ -242,6 +244,7 @@ describe Gitlab::GitAccess, lib: true do
             else
               project.team << [user, role]
             end
+          end
 
           permissions_matrix[role].each do |action, allowed|
             context action do
@@ -259,7 +262,6 @@ describe Gitlab::GitAccess, lib: true do
         end
       end
     end
-    end
 
     # Run permission checks for a group
     def self.run_group_permission_checks(permissions_matrix)