Make SNS topic policy Action a list, update ID

The previous attempt to deploy failed:

- https://github.com/mbland/elistman/actions/runs/4661623744/jobs/8251134356

  UPDATE_FAILED
  AWS::SES::ConfigurationSetEventDestination
  SendingConfigurationSetDestination
  Resource handler returned message: "Could not publish message to SNS
  topic <arn:aws:sns:us-east-1:***:elistman-dev>. (Service: SesV2,
  Status Code: 400, Request ID: ...)" (RequestToken: ...,
  HandlerErrorCode: InvalidRequest)

I think it might be because "Action" should've been a list of string,
not just a string. We'll see.

Also decided to give the PolicyDocument a unique ID, to possibly avoid a
similar problem to the conflict noted in commit
d85327c.

template.yml

@@ -177,12 +177,13 @@ Resources:
       PolicyDocument:
           # https://docs.aws.amazon.com/ses/latest/dg/configure-sns-notifications.html#configure-feedback-notifications-prerequisites
           Version: 2012-10-17
-          Id: notification-policy
+          Id: !Sub "${AWS::StackName}-notification-policy"
           Statement:
             - Effect: Allow
               Principal:
                 Service: ses.amazonaws.com
-              Action: "sns:Publish"
+              Action:
+                - "sns:Publish"
               Resource: !Ref DeliveryNotificationsTopic
               Condition:
                 StringEquals: