[INLONG-4205][CI] Fix error in the greeting workflow

[shink]

fix: #4205

Motivation

Fix error in the greeting workflow.

The pull_request_target event is similar to pull_request, except that it runs in the context of the base repository of the pull request, rather than in the merge commit. This means that you can more safely make your secrets available to the workflows triggered by the pull request, because only workflows defined in the commit on the base repository are run. For example, this event allows you to create workflows that label and comment on pull requests, based on the contents of the event payload.

reference:

• Error: Resource not accessible by Integration actions/first-interaction#31
• https://securitylab.github.com/research/github-actions-preventing-pwn-requests/

Modifications

• replace pull_request with pull_request_target