sql: Fix TestCancelQueriesRace

TestCancelQueriesRace attempts to run two query cancellations
at the same time in order to reproduce potential data race.
However, it makes an invalid assumption that both query cancellations
will always succeed which is not true. This PR updates the check
to ensure that at least one of the query cancellations is successful.

Epic: none
Fixes: #95718
Release note: none

pkg/sql/show_test.go

@@ -1341,14 +1341,18 @@ func TestCancelQueriesRace(t *testing.T) {
 		_, _ = sqlDB.ExecContext(ctx, `SELECT pg_sleep(10)`)
 		close(waiter)
 	}()
-	_, err := sqlDB.ExecContext(ctx, `CANCEL QUERIES (
+	_, err1 := sqlDB.ExecContext(ctx, `CANCEL QUERIES (
 		SELECT query_id FROM [SHOW QUERIES] WHERE query LIKE 'SELECT pg_sleep%'
 	)`)
-	require.NoError(t, err)
-	_, err = sqlDB.ExecContext(ctx, `CANCEL QUERIES (
+
+	_, err2 := sqlDB.ExecContext(ctx, `CANCEL QUERIES (
 		SELECT query_id FROM [SHOW QUERIES] WHERE query LIKE 'SELECT pg_sleep%'
 	)`)
-	require.NoError(t, err)
+	// At least one query cancellation is expected to succeed.
+	require.Truef(
+		t,
+		err1 == nil || err2 == nil,
+		"Both query cancellations failed with errors: %v and %v", err1, err2)
 
 	cancel()
 	<-waiter