ci: don't allow specifying a branch

Author: merceyz

.github/workflows/release-branch.yml

@@ -1,10 +1,5 @@
 on:
   workflow_dispatch:
-    inputs:
-      branch:
-        description: 'Branch?'
-        required: true
-        default: 'cherry-pick/'
 
 name: 'Release Branch'
 jobs:
@@ -18,7 +13,6 @@ jobs:
     steps:
     - uses: actions/checkout@v3
       with:
-        ref: ${{github.event.inputs.branch}}
         token: ${{secrets.YARNBOT_TOKEN}}
 
     - name: 'Retrieve all the relevant tags'