Change docs to reflect mute_time_intervals in routes instead of mute_times
Change docs to reflect mute_time_intervals in routes instead of mute_times

Signed-off-by: Ben Ridley <355023fe1c8f86a7ebed12a304e34c56a0753505@gmail.com>

prometheus/alertmanager,prometheus/alertmanager,prometheus/alertmanager,GoogleCloudPlatform/alertmanager,GoogleCloudPlatform/alertmanager,GoogleCloudPlatform/alertmanager,GoogleCloudPlatform/alertmanager,prometheus/alertmanager