chore(docs): fix incorrect WAF monitoring function name in README [skip ci] (#359)

`monitorWebApplicationFirewallAcl` has been renamed to `monitorWebApplicationFirewallAclV2` in previous versions probably not still shows the wrong function name in docs

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_By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license_

Author: hassanazharkhan

README.md

@@ -93,7 +93,7 @@ You can browse the documentation at https://constructs.dev/packages/cdk-monitori
 | AWS SNS Topic (`.monitorSnsTopic()`) | Message count, size, failed notifications | Failed notifications, min/max published messages | |
 | AWS SQS Queue (`.monitorSqsQueue()`, `.monitorSqsQueueWithDlq()`) | Message count, age, size | Message count, age, DLQ incoming messages | |
 | AWS Step Functions (`.monitorStepFunction()`, `.monitorStepFunctionActivity()`, `monitorStepFunctionLambdaIntegration()`, `.monitorStepFunctionServiceIntegration()`) | Execution count and breakdown per state | Duration, failed, failed rate, aborted, throttled, timed out executions | |
-| AWS Web Application Firewall (`.monitorWebApplicationFirewallAcl()`) | Allowed/blocked requests | Blocked requests count/rate | |
+| AWS Web Application Firewall (`.monitorWebApplicationFirewallAclV2()`) | Allowed/blocked requests | Blocked requests count/rate | |
 | Custom metrics (`.monitorCustom()`) | Addition of custom metrics into the dashboard (each group is a widget) | | Supports anomaly detection |