Refactor github-token input to use CUSTOM_GH_TOKEN secret for authentication in runner-fallback action

.github/actions/runner-fallback/action.yml

@@ -10,6 +10,10 @@ inputs:
   fallback-runner:
     description: 'Comma-separated label list or single label for the fallback (e.g. "ubuntu-latest")'
     required: true
+  github-token:
+    description: 'GitHub token with repo admin read permissions'
+    required: false
+    default: ${{ secrets.CUSTOM_GH_TOKEN }}
 
 outputs:
   use-runner:
@@ -23,9 +27,7 @@ runs:
       id: pick
       shell: bash
       env:
-        # token needs to have reop admin read permissions
-        # https://docs.github.com/en/rest/actions/self-hosted-runners?apiVersion=2022-11-28#list-self-hosted-runners-for-a-repository
-        TOKEN: ${{ secrets.CUSTOM_GH_TOKEN }}
+        TOKEN: ${{ inputs.github-token }}
         PRIMARY: ${{ inputs.primary-runner }}
         FALLBACK: ${{ inputs.fallback-runner }}
       run: |