fix: Update controller tests with valid config

The previous commit introduced a unified and validated configuration
for the flow control system, requiring callers to pass a pre-validated
cofig to the controller and registry respectively. This change updates
the controller tests to provide a valid configuration instead of relying
on the now-removed defaulting logic in the constructor.

Author: LukeAVanDrie

pkg/epp/flowcontrol/controller/controller_test.go

@@ -796,6 +796,7 @@ func TestFlowController_Concurrency(t *testing.T) {
 		// Use a generous buffer to prevent flakes in the test due to transient queuing delays.
 		EnqueueChannelBufferSize: numRequests,
 		DefaultRequestTTL:        1 * time.Second,
+		ExpiryCleanupInterval:    100 * time.Millisecond,
 	}, mockRegistry)
 
 	var wg sync.WaitGroup