Allow only string paths, not byte paths

These paths can flow into `shutil.move`, which does not accept byte
paths or (int) file descriptors.  See python/typeshed#6832

Author: eaftan

src/dotenv/main.py

@@ -305,7 +305,7 @@ def _is_interactive():
 
 
 def load_dotenv(
-    dotenv_path: Optional[Union[str, bytes, 'os.PathLike[Union[str, bytes]]', int]] = None,
+    dotenv_path: Optional[Union[str, 'os.PathLike[str]']] = None,
     stream: Optional[IO[str]] = None,
     verbose: bool = False,
     override: bool = False,