[bug] MetricReaderExt.RemoveMetric is failing in certain unit tests

[TimothyMothra]

Package

OpenTelemetry

Package Version

main branch

Runtime Version

net462

Description

Some tests are failing when running locally.

• OpenTelemetry.Extensions.Hosting.Tests (net462)
  • OpenTelemetryMetricsBuilderExtensionsTests.ReloadOfMetricsViaIConfigurationWithoutExportCleanupTest
    This is failing on every run.
• OpenTelemetry.Tests (net462)
  I haven't identified the exact test that is failing here. Seems to be intermittent.

Seems to be hitting this condition:

opentelemetry-dotnet/src/OpenTelemetry/Metrics/Reader/MetricReaderExt.cs

Lines 271 to 272 in cddc091

	var result = this.instrumentIdentityToMetric.TryRemove(metric.InstrumentIdentity, out var _);
	Debug.Assert(result, "result was false");

Steps to Reproduce

Run unit test locally

Expected Result

N/A

Actual Result

N/A

Additional Context

This was first reported here #5890