Add execute-api to SCP Not-Deny Action for WebSocket API

[YutaOkoshi]

PR Summary

I encountered an error when attempting to connect a WebSocket using a Sandbox account.
This was because the execute-api:ManageConnections command was being denied via SCP.

An error occurred (AccessDeniedException) when calling the PostToConnection operation: 
User: arn:aws:sts::123412341234:assumed-role/websocket-handler-role-enk7x5b2/websocket-handler
is not authorized to perform: execute-api:ManageConnections on resource: 
arn:aws:execute-api:us-east-1:********8190:zgeh0r2vv1/prod/POST/@connections/{connectionId} 
with an explicit deny in a service control policy

This PR adds execute-api to the AWS Nuke supported services list, enabling proper cleanup of WebSocket API resources.

Changes

Added execute-api:* to isb-aws-nuke-supported-services-scp.json

Updated corresponding test snapshots

Technical Background (from AWS official documentation)

1. Automatic Disconnection of WebSocket Connections
   WebSocket connections are automatically disconnected after a 10-minute idle timeout:

API Gateway returns this status code when the client is idle for 10 minutes or reaches the maximum 2-hour connection lifetime.
Reference URL: https://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-websocket-api-overview.html

2. Regarding the Definition of execute-api:ManageConnections
   execute-api:ManageConnections is defined as an action, not a resource:

The execute-api action supports ManageConnections in addition to existing actions (Invoke, InvalidateCache). ManageConnections controls access to the @connections API.
Reference URL: https://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-websocket-control-access-iam.html

3. AWS Nuke Behavior
   AWS Nuke does not target actions for deletion, so the execute-api:ManageConnections action itself will not be deleted. However, deleting the WebSocket API resource prevents new connections and existing connections will automatically time out and disconnect.

Expected Effects

• Proper cleanup of the WebSocket API resource
• Automatic disconnection of existing connections via a 10-minute timeout
• This error will be resolved.

An error occurred (AccessDeniedException) when calling the PostToConnection operation: 
User: arn:aws:sts::123412341234:assumed-role/websocket-handler-role-enk7x5b2/websocket-handler
is not authorized to perform: execute-api:ManageConnections on resource: 
arn:aws:execute-api:us-east-1:********8190:zgeh0r2vv1/prod/POST/@connections/{connectionId} 
with an explicit deny in a service control policy

[YutaOkoshi]

@aws-khargita
I tried to set up a WebSocket but got rejected by SCP, so I came up with this fix. Feel free to use it if it works for you.

[aws-khargita]

@YutaOkoshi Thanks for opening this PR! Will make sure it is incorporated in the next non-patch release.