Fix wheels-docker workflow: remove source dist copy

The wheels-docker workflow should only build manylinux wheels,
not source distributions. Source distribution is built separately
in wheels.yml on Linux x86_64 only.

Removed lines attempting to copy dist/*.tar.gz which doesn't exist
in this workflow, causing build failures.

Author: oberstet

.github/workflows/wheels-docker.yml

@@ -217,8 +217,6 @@ jobs:
               cp "$wheel" wheelhouse/
             fi
           done
-          echo "Copying source distribution"
-          cp dist/*.tar.gz wheelhouse/
 
           echo ""
           echo "==> Final wheel inventory after manylinux conversion:"