tests/resource/aws_cloudwatch_metric_alarm: Blacklist usw2-az4 AZ for instance testing (#11957)
tests/resource/aws_cloudwatch_metric_alarm: Blacklist usw2-az4 AZ for instance testing (#11957)

Previously in the acceptance testing:

```
--- FAIL: TestAccAWSCloudWatchMetricAlarm_AlarmActions_EC2Automate (9.91s)
    testing.go:640: Step 0 error: errors during apply:

        Error: Error launching source instance: Unsupported: Your requested instance type (t2.micro) is not supported in your requested Availability Zone (us-west-2d). Please retry your request by not specifying an Availability Zone or choosing us-west-2a, us-west-2b, us-west-2c.
```

Output from acceptance testing:

```
--- PASS: TestAccAWSCloudWatchMetricAlarm_AlarmActions_EC2Automate (217.91s)
```
kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,kjmkznr/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws