chore(build): fix extension module hash calculation (#14195)

On Python versions prior to 3.13, the following returns 0

```
python -c "from pathlib import Path; print(sum(1 for p in Path('.').rglob('**') if p.suffix and p.suffix in {'.cpp', '.hpp'}))"
```

Because `Path('.').rglob(**)` returns only directories on older
versions, but on Python 3.13 it returns all files and dirs.

This resulted in incorrect computation for extension hashes


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Author: taegyunkim

setup.py

@@ -662,7 +662,7 @@ def get_sources(self, cmd: build_ext) -> t.List[Path]:
         return (
             [
                 _
-                for _ in Path(self.source_dir).rglob("**")
+                for _ in Path(self.source_dir).glob("**/*")
                 if _.is_file() and _.name != full_path.name and _.suffix and _.suffix not in {".py", ".pyc", ".pyi"}
             ]
             if self.source_dir