sql: fix insight integration test for contention

This change lowers the latency threshold for which
statement is considered slow to make sure it detects
contention.
Previous value was set to 100ms which is default. New
value is set to 30ms to be the same as overridden
value in other tests.

Release note: None

Author: koorosh

pkg/sql/sqlstats/insights/integration/insights_test.go

@@ -523,7 +523,7 @@ func TestInsightsIntegrationForContention(t *testing.T) {
 	require.NoError(t, err)
 
 	// Enable detection by setting a latencyThreshold > 0.
-	latencyThreshold := 100 * time.Millisecond
+	latencyThreshold := 30 * time.Millisecond
 	insights.LatencyThreshold.Override(ctx, &settings.SV, latencyThreshold)
 
 	// Create a new connection, and then in a go routine have it start a transaction, update a row,