ci(security): check for pull_request_target events in the access check

[zimeg]

Summary

This PR updates the access_check to check that the event is a a pull_request_target instead of a pull_request.

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[filmaj]

What's the difference / implication of this change?

[zimeg]

@filmaj Right now the access_check checks if the event_name is pull_request but the event that's starting this workflow is pull_request_target, so the check evaluates to false (meaning the access check passes unexpectedly).

[zimeg]

@filmaj Thank you once again for the quick review 🙌 🙇