Add repo input to reftest generator action (#4356)

.github/workflows/generate_vectors.yml

@@ -7,6 +7,11 @@ defaults:
 on:
   workflow_dispatch:
     inputs:
+      repo:
+        description: The repository to use (e.g. user/consensus-specs)
+        default: ethereum/consensus-specs
+        type: string
+        required: true
       ref:
         description: The branch, tag or SHA to checkout and build from
         default: dev
@@ -23,9 +28,9 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
-          repository: 'ethereum/consensus-specs'
+          repository: ${{ inputs.repo }}
           path: 'consensus-specs'
-          ref: ${{ inputs.ref || 'dev' }}
+          ref: ${{ inputs.ref }}
       - name: Setup Python
         uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
         with: