[cmd/telemetrygen] Flaky TestRateOfMetrics on Windows

[mx-psi]

Component(s)

cmd/telemetrygen

Describe the issue you're reporting

The windows-unittest-matrix (other) job has recently failed on main on the TestRateOfMetrics from cmd/telemetrygen after merging #21629 (not sure if related)

2023-08-07T10:05:04.709Z	INFO	metrics/metrics.go:92	generation of metrics isn't being throttled
2023-08-07T10:05:04.772Z	INFO	metrics/worker.go:67	metrics generated	{"worker": 0, "metrics": 5}
--- FAIL: TestRateOfMetrics (0.55s)
    worker_test.go:81: 
        	Error Trace:	D:/a/opentelemetry-collector-contrib/opentelemetry-collector-contrib/cmd/telemetrygen/internal/metrics/worker_test.go:81
        	Error:      	Should be true
        	Test:       	TestRateOfMetrics
        	Messages:   	there should have been more than 6 metrics, had 5
2023-08-07T10:05:06.380Z	INFO	metrics/metrics.go:92	generation of metrics isn't being throttled
2023-08-07T10:05:07.478Z	INFO	metrics/worker.go:67	metrics generated	{"worker": 0, "metrics": 151879}
FAIL
FAIL	github.com/open-telemetry/opentelemetry-collector-contrib/cmd/telemetrygen/internal/metrics	2.857s
ok  	github.com/open-telemetry/opentelemetry-collector-contrib/cmd/telemetrygen/internal/traces	1.632s
FAIL

We should fix this!

[mx-psi]

Closing as duplicate of #21212, sorry!