simplify typing

- connsider `local_config["readme"]` as `str | Iterable[str]` in sdist

Author: wagnerluis1982

src/poetry/core/masonry/builders/sdist.py

@@ -333,8 +333,8 @@ def find_files_to_add(self, exclude_build: bool = False) -> set[BuildIncludeFile
 
         # add readme files if it is specified
         if "readme" in self._poetry.local_config:
-            r: str | Path | Iterable[str | Path] = self._poetry.local_config["readme"]
-            if isinstance(r, (str, Path)):
+            r: str | Iterable[str] = self._poetry.local_config["readme"]
+            if isinstance(r, str):
                 additional_files.add(r)
             else:
                 additional_files.update(r)