workflows: Fix tag name for release sources job (llvm#100752)

(cherry picked from commit 3c2ce70)

Author: tstellar

.github/workflows/release-sources.yml

@@ -51,7 +51,7 @@ jobs:
     steps:
       - id: inputs
         run: |
-          ref=${{ inputs.release-version || github.sha }}
+          ref=${{ (inputs.release-version && format('llvmorg-{0}', inputs.release-version)) || github.sha }}
           if [ -n "${{ inputs.release-version }}" ]; then
             export_args="-release ${{ inputs.release-version }} -final"
           else