fix(ci): use pull_request_target for PR actions (#2065)

For the actions that create a PR, use the `pull_request_target` event so
that they can run with write permissions when triggered by pull requests
that originate from a fork.

Author: andogq

.github/workflows/create-cut-pr.yml

@@ -1,7 +1,7 @@
 name: Create cut PR
 
 on:
-  pull_request:
+  pull_request_target:
     types:
       - closed
     branches:

.github/workflows/create-release-pr.yml

@@ -1,7 +1,7 @@
 name: Create release PR
 
 on:
-  pull_request:
+  pull_request_target:
     types:
       - closed
     branches: