test(flowcontrol): correct FullPath backpressure comment

The inline comment claimed the FullPath benchmark sustains W>L queuing, but
worker count rounds down to <= L and the real detector's in-flight load is
released near-instantly, so dispatch is effectively free-flowing. Reword to
match the function godoc: FullPath prices dispatch + the detector's per-cycle
DynamicAttribute reads, not sustained backpressure.

Signed-off-by: Luke Van Drie <lukevandrie@google.com>

Author: LukeAVanDrie

pkg/epp/flowcontrol/benchmark/benchmark_test.go

@@ -304,9 +304,10 @@ func BenchmarkFlowController_FullPath(b *testing.B) {
 
 	telemetry := newBenchmarkTelemetry()
 
-	// Concurrency-gated: each dispatched request consumes a detector slot and
-	// releases it after ResponseBody, so W workers > L limit sustains backpressure
-	// and forces real queuing in the dispatch cycle.
+	// Concurrency-gated by the real detector: each dispatched request records in-flight load (via
+	// PreRequest) and releases it after ResponseBody. Load is held only briefly, so this measures
+	// free-flowing dispatch plus the detector's per-cycle DynamicAttribute read cost rather than
+	// sustained W>L queuing.
 	var globalReqID atomic.Uint64
 
 	b.ResetTimer()