Try fixing windows artifact output again (#7637)

The [previous] change assumed that the shell is powershell, but the shell is actually commands (cmd). 

The [previous] change assumed we're in the root directory.  This assumption is probably correct [ref]. So we keep that change.

[ref]:  https://github.com/google/filament/blob/main/build/windows/build-github.bat#L134
[previous]: 373c5710b1

.github/workflows/release.yml

@@ -205,7 +205,7 @@ jobs:
           TAG: ${{ steps.git_ref.outputs.tag }}
         run: |
           build\windows\build-github.bat release
-          move out\filament-windows.tgz out\filament-$Env:TAG-windows.tgz
+          move out\filament-windows.tgz out\filament-%TAG%-windows.tgz
         shell: cmd
       - uses: actions/github-script@v6
         env: