Remove flaky dial throttler tests

[aaronbuchwald]

Resolves #4138

Each of these tests are race conditions. We could modify them, but decided on Slack to remove.

At least the failing cancellation test could be re-written to avoid a race condition:

func TestDialThrottlerCancel(t *testing.T) {
	require := require.New(t)

	// Allows 5 per second
	throttler := NewDialThrottler(5)

	acquiredChan := make(chan error, 1)
	ctx, cancel := context.WithCancel(context.Background())
	cancel()

	// Throttler should return a cancellation error immediately since
	// the context was already cancelled.
	acquiredChan <- throttler.Acquire(ctx)
	require.ErrorIs(<-acquiredChan, context.Canceled)
}

Will leave for PR review if we want to question this and re-write instead.

[Copilot]

Pull Request Overview

This PR removes flaky dial throttler tests that contain race conditions as identified in issue #4138. The team decided to remove these problematic tests rather than attempting to fix them, though an example fix for the cancellation test is provided in the PR description for future consideration.

• Removes three test functions that were causing flaky test failures due to race conditions
• Eliminates timing-dependent assertions that were unreliable in CI environments
• Deletes the entire test file since all tests were problematic

Comments suppressed due to low confidence (1)