Switch release_candidate workflow to workflow_dispatch

.github/workflows/release-candidate.yml

@@ -1,9 +1,6 @@
 name: Release candidate
 
-on:
-  push:
-    branches:
-    - 'rc/**'
+on: workflow_dispatch
 
 permissions:
   contents: read

RELEASE-CHECKLIST

@@ -2,7 +2,7 @@
 [ ] make prerelease
 [ ] Finalize changelog
 [ ] Update AUTHORS (make authors LASTRELEASE=x.y.z)
-[ ] push release candidate branch rc/VERSION
+[ ] Run release candidate workflow manually on GitHub
 [ ] if it builds successfully, download artifacts
 [ ] run tools/build-arm.sh to create and download arm64 linux package
 [ ] Use 'make' in macos and windows artifacts to sign code