CloudWatch Monitoring Dashboard doesn't show WAF metrics

[kyoicito]

Describe the bug The template includes the resource MonitoringDashboard which means to monitor WAF metrics, but it specifies incorrect Namespace and WebACL dimension.

To Reproduce Run Security Automations and access to the dashboard.

Expected behavior CloudWatch Dashboard shows WAF metrics.

Please complete the following information about the solution:

• [ ] Version: v3.2.3
• [ ] Region: ap-northeast-1
• [N/A] Was the solution modified from the version published on this repository?
• [N/A] If the answer to the previous question was yes, are the changes available on GitHub?
• [N/A] Have you checked your service quotas for the sevices this solution uses?
• [N/A] Were there any errors in the CloudWatch Logs?

Screenshots If applicable, add screenshots to help explain your problem (please DO NOT include sensitive information).

Additional context I'll put PR for this issue.

[kyoicito]

Sorry, I found this issue is duplicated as #145. I'll close this issue and associate PR #231 to #145.