Do not set UV_BINARY on Windows

Absolute paths here confuse n2 - can be possibly fixed by quoting

CI error:
```
 n2: error: parse error: expected '\n', got ':'
out\build.ninja:79: ...ronment  | $runner C:\hostedtoolcache\wi...
```

.github/actions/setup-anki/action.yml

@@ -90,6 +90,7 @@ runs:
 
     # UV_BINARY tells the build system to use our uv instead of downloading its own
     - name: Set UV_BINARY
+      if: runner.os != 'Windows'
       shell: bash
       run: echo "UV_BINARY=${{ steps.setup-uv.outputs.uv-path }}" >> "$GITHUB_ENV"