Replace pull_request_target with pull_request

[Sandhya1236]

Hi all,

Please replace insecure usage of pull_request_target. Here is at least one instance:

meta-ar/.github/workflows/pre_merge_build.yml

Line 6 in fa00a12

pull_request_target: # requiring access to base repo

We have pull_request_target guidance and suggested alternatives on the OSDO site at go/github-pull-request-target.

I have limited pull requests to internal QC members only for the time being until this is addressed. Reach out to go/ossops if you have questions or concerns.

Thanks,
Sandhya