move labeller to separate workflow with pull_request_target

Author: WillCorrigan

.github/workflows/label.yml

@@ -0,0 +1,16 @@
+name: label
+on: pull_request_target
+
+jobs:
+  labeller:
+    permissions:
+      contents: read
+      pull-requests: write
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        fetch-depth: 2
+    - uses: actions/labeler@v5
+      with:
+        sync-labels: true

.github/workflows/pr.yml

@@ -2,18 +2,6 @@ name: PR
 on: pull_request
 
 jobs:
-  labeller:
-    permissions:
-      contents: read
-      pull-requests: write
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v4
-      with:
-        fetch-depth: 2
-    - uses: actions/labeler@v5
-      with:
-        sync-labels: true
   test:
     runs-on: ubuntu-latest
     steps: