Clarify in resource docs that value defaults to 0 (#3095)

Author: AgustinBettati

docs/resources/maintenance_window.md

@@ -36,7 +36,7 @@ Once maintenance is scheduled for your cluster, you cannot change your maintenan
 
 * `project_id` - The unique identifier of the project for the Maintenance Window.
 * `day_of_week` - (Required) Day of the week when you would like the maintenance window to start as a 1-based integer: Su=1, M=2, T=3, W=4, T=5, F=6, Sa=7.
-* `hour_of_day` - Hour of the day when you would like the maintenance window to start. This parameter uses the 24-hour clock, where midnight is 0, noon is 12 (Time zone is UTC).
+* `hour_of_day` - Hour of the day when you would like the maintenance window to start. This parameter uses the 24-hour clock, where midnight is 0, noon is 12 (Time zone is UTC). Defaults to 0.
 * `start_asap` - Flag indicating whether project maintenance has been directed to start immediately. If you request that maintenance begin immediately, this field returns true from the time the request was made until the time the maintenance event completes.
 * `defer` - Defer the next scheduled maintenance for the given project for one week.
 * `auto_defer` - Defer any scheduled maintenance for the given project for one week.