ci: don't use pull_request_target with semantic PR title check

[dsanders11]

Description of Change

pull_request_target has sharp edges like granting access to secrets so it shouldn't be used unless necessary. pull_request should work fine here.

Checklist

• PR description included and stakeholders cc'd

Release Notes

Notes: none

[codebytere]

To my understanding pull_request_target is only necessary when we need read/write permissions on forks, which isn't relevant here, so this seems fine to me too!

[release-clerk]

No Release Notes