Mitigate pull_request_target privilege escalation

Hotfix — replaces pull_request_target with pull_request to stop
granting write permissions and secrets to fork PRs. Some workflows
will break; can be fixed properly later.

.github/workflows/pull-request-conflict.yml

@@ -4,7 +4,7 @@ on:
   push:
     branches:
       - master
-  pull_request_target:
+  pull_request:
   issue_comment:
 
 permissions: {}
@@ -16,7 +16,7 @@ jobs:
     steps:
       - name: Apply label
         uses: eps1lon/actions-label-merge-conflict@1df065ebe6e3310545d4f4c4e862e43bdca146f0 # v3.0.3
-        if: ${{ github.event_name == 'push' || github.event_name == 'pull_request_target'}}
+        if: ${{ github.event_name == 'push' || github.event_name == 'pull_request'}}
         with:
           dirtyLabel: 'merge conflict'
           commentOnDirty: 'This pull request has merge conflicts. Please resolve the conflicts so the PR can be successfully reviewed and merged.'