DEV: Don’t replace Rails logger in specs (#29721)

Instead of replacing the Rails logger in specs, we can instead use
`#broadcast_to` which has been introduced in Rails 7.

plugins/automation/spec/scripts/topic_spec.rb

@@ -167,12 +167,11 @@ describe "Topic" do
     end
 
     context "when creating the post fails" do
-      before do
-        @orig_logger = Rails.logger
-        Rails.logger = @fake_logger = FakeLogger.new
-      end
+      let(:fake_logger) { FakeLogger.new }
 
-      after { Rails.logger = @orig_logger }
+      before { Rails.logger.broadcast_to(fake_logger) }
+
+      after { Rails.logger.stop_broadcasting_to(fake_logger) }
 
       it "logs a warning" do
         expect { UserUpdater.new(user, user).update(location: "Japan") }.to change {