Switch pull_request_target to workflow_dispatch

Manually trigger preversion updates. Ideally this would be
pull_request_target, but not sure how to pass manual inputs to that
trigger.

.github/workflows/workflow-version_task-semverGithub.yml

@@ -5,8 +5,22 @@
 #   - main branch is protected
 name: Bump version
 on:
-  pull_request_target:
-    types: [closed]
+  workflow_call:
+    inputs:
+      comments:
+        description: Comments
+        required: false
+        type: string
+      project-metadata:
+        description: File containing project metadata (e.g. pyproject.toml)
+        required: false
+        default: pyproject.toml
+        type: string
+      pipeline-description:
+        description: Boolean flag to update pipeline_description.json
+        required: false
+        default: false
+        type: boolean
   workflow_call:
     inputs:
       project-metadata: