resource/alicloud_alidns_cloud_gtm_monitor_template: drop 0 from failure_rate enum

[api-tool-agent]

What does this PR do?

The failure_rate argument of the alicloud_alidns_cloud_gtm_monitor_template resource accepted 0 in its ValidateFunc, but the backing APIs (CreateCloudGtmMonitorTemplate / UpdateCloudGtmMonitorTemplate) only support 20 / 50 / 80 / 100. This removes 0 from the valid set so that invalid configurations fail at plan time instead of being sent to the API and rejected there.

Test results

All acceptance tests pass:

=== RUN TestAccAliCloudAlidnsCloudGtmMonitorTemplate_basic12684
--- PASS: TestAccAliCloudAlidnsCloudGtmMonitorTemplate_basic12684 (5.69s)

=== RUN TestAccAliCloudAlidnsCloudGtmMonitorTemplate_basic12685
--- PASS: TestAccAliCloudAlidnsCloudGtmMonitorTemplate_basic12685 (11.21s)

=== RUN TestAccAliCloudAlidnsCloudGtmMonitorTemplate_basic12690
--- PASS: TestAccAliCloudAlidnsCloudGtmMonitorTemplate_basic12690 (8.28s)

=== RUN TestAccAliCloudAlidnsCloudGtmMonitorTemplate_basic12691
--- PASS: TestAccAliCloudAlidnsCloudGtmMonitorTemplate_basic12691 (5.78s)

=== RUN TestAccAliCloudAlidnsCloudGtmMonitorTemplate_failureRateEnum
--- PASS: TestAccAliCloudAlidnsCloudGtmMonitorTemplate_failureRateEnum (5.01s)

A new acceptance test TestAccAliCloudAlidnsCloudGtmMonitorTemplate_failureRateEnum is added to cover the enum change: failure_rate=100 is accepted at create, while failure_rate=0 is rejected by validation with expected failure_rate to be one of [20 50 80 100].