Revise type of dotenv_path parameter

Based on PR feedback and typeshed's type hint for the built-in open()
function:
https://github.com/python/typeshed/blob/e2d67bf7034f68c07bd35150247e58e0817725d9/stdlib/builtins.pyi#L1421

src/dotenv/main.py

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