Received ''null' values are not allowed in templates'' while creating AWS::Events::Rule -> EventPattern

### Name of the resource

AWS::Events::Rule

### Resource Name

_No response_

### Issue Description

EventPattern accepts Null value as per EventBridge service [1] ,even CDK documentation [2] mention that EventPattern can have null values. However CloudFormation service does not accept Null value when defined for EventPattern. Template fails in validation with following error - 'null' values are not allowed in templates

[1] https://docs.aws.amazon.com/eventbridge/latest/userguide/eb-event-patterns-null-values.html
[2] https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_events.EventPattern.html

### Expected Behavior

AWS::Events::Rule should accept null values for 'EventPattern' property

### Observed Behavior

template does not pass validation and throws error - 'null' values are not allowed in templates

### Test Cases

Create EventBridge rule with EventPattern having null value in CFN template

### Other Details

_No response_

Start by reproducing the AWS::Events::Rule validation failure with an EventPattern containing a null value, then compare the behavior with the linked EventBridge and CDK documentation. Done means CloudFormation accepts the documented null value in EventPattern without the template validation error.

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