Attempt to fix flaky threaded worker logging test (#4419)

This test occasionally fails in CI with:
`can't convert RSpec::Mocks::Double to Hash (RSpec::Mocks::Double#to_hash gives RSpec::Mocks::Double)`

It is difficult to reproduce, but I think that using a true Hash instead of a spy may make it more reliable

Example failure:
https://github.com/cloudfoundry/cloud_controller_ng/actions/runs/15833920407/job/44685199774?pr=4416

Author: tcdowney

spec/unit/lib/delayed_job/threaded_worker_spec.rb

@@ -64,7 +64,8 @@
     end
 
     it 'sets the worker name in the Steno context' do
-      steno_data_spy = spy('data')
+      steno_data_spy = {}
+      allow(steno_data_spy).to receive(:[]=).and_call_original
       allow(Steno.config.context).to receive(:data).and_return(steno_data_spy)
 
       worker.start