Increase sleep time for install progress tests (#3493)

Increase the sleep timeout for testcase `TestProgress/single_step_delayed_failure`
to avoid flakiness on Windows.
The tick interval for the test is set to 10 ms but the code allows for
variance between 65% and 250% of such value and it expects at least 1
tick to happen (it is asserted on the regexp match as at least 1
additional `.`)

Original sleep time of 15 ms would not cover the whole possible
interval, after testing on windows with different timings the most
reliable seems to be ~100ms (40-50 ms would still yield a few failures
when run 10000 times in a loop)

internal/pkg/agent/install/progress_test.go

@@ -51,7 +51,7 @@ func TestProgress(t *testing.T) {
 		rs := pt.Start()
 
 		s := rs.StepStart("step 1 starting")
-		time.Sleep(15 * time.Millisecond) // to simulate work being done
+		time.Sleep(100 * time.Millisecond) // to simulate work being done
 		s.Failed()
 
 		rs.Failed()