util/retry: increase timing tolerance for cancellation tests

The TestRetryWithMaxDuration test was flaky because the timing expectations
were too strict for test cases involving context cancellation and closer
channel closure. When these cancellation mechanisms are triggered during
a retry backoff period, the retry loop may not exit immediately, leading
to timing variance that exceeded the previous 20ms limit.

Increased maxExpectedTimeSpent from 20ms to 30ms for both:
- "errors with context that is canceled"
- "errors with opt.Closer that is closed"

This provides sufficient buffer for the inherent timing variability while
still validating that cancellation works promptly.

Fixes #154764

Author: sanki92

pkg/util/retry/retry_test.go

@@ -474,7 +474,7 @@ func TestRetryWithMaxDuration(t *testing.T) {
 			preRetryFunc: func() {
 				cancelCtxFunc()
 			},
-			maxExpectedTimeSpent: time.Millisecond * 20,
+			maxExpectedTimeSpent: time.Millisecond * 30,
 			expectedErr:          true,
 			// Under duress, closing a context will not necessarily stop the retry
 			// loop immediately, so we skip this test under duress.
@@ -494,7 +494,7 @@ func TestRetryWithMaxDuration(t *testing.T) {
 			preRetryFunc: func() {
 				close(closeCh)
 			},
-			maxExpectedTimeSpent: time.Millisecond * 20,
+			maxExpectedTimeSpent: time.Millisecond * 30,
 			expectedErr:          true,
 			// Under duress, closing a channel will not necessarily stop the retry
 			// loop immediately, so we skip this test under duress.