ci: remove GitHub CI — native git.hanzo.ai + cd.hanzo.ai only

This workflow ran on a self-hosted actions-runner-controller pool. ARC is
decommissioned: CI executes inside git.hanzo.ai (Gitea Actions, .hanzo/workflows)
and delivery is cd.hanzo.ai reconciling the reviewed image pin in
hanzoai/universe. GitHub is a mirror and runs nothing.

Removed rather than repointed — there is no GitHub-side pool to move to, and
leaving it would keep ARC load-bearing.

.github/workflows/release_notes.yml

@@ -1,42 +0,0 @@
-# This action:
-#
-# 1. Generates release notes using github API.
-# 2. Strips unnecessary info like chore/style etc from notes.
-# 3. Updates release info.
-
-# This action needs to be maintained on all branches that do releases.
-
-name: 'Release Notes'
-
-on:
-  workflow_dispatch:
-    inputs:
-      tag_name:
-        description: 'Tag of release like v13.0.0'
-        required: true
-        type: string
-  release:
-    types: [released]
-
-permissions:
-  contents: read
-
-jobs:
-  regen-notes:
-    name: 'Regenerate release notes'
-    runs-on: hanzo-build-linux-amd64
-
-    steps:
-    - name: Update notes
-      run: |
-        NEW_NOTES=$(gh api --method POST -H "Accept: application/vnd.github+json"  /repos/frappe/erpnext/releases/generate-notes  -f tag_name=$RELEASE_TAG \
-          | jq -r '.body' \
-          | sed -E '/^\* (chore|ci|test|docs|style)/d' \
-          | sed -E 's/by @mergify //'
-        )
-        RELEASE_ID=$(gh api -H "Accept: application/vnd.github+json" /repos/frappe/erpnext/releases/tags/$RELEASE_TAG | jq -r '.id')
-        gh api --method PATCH -H "Accept: application/vnd.github+json" /repos/frappe/erpnext/releases/$RELEASE_ID -f body="$NEW_NOTES"
-
-      env:
-        GH_TOKEN: ${{ secrets.RELEASE_TOKEN }}
-        RELEASE_TAG: ${{ github.event.inputs.tag_name || github.event.release.tag_name }}