zipimporter.get_data returns bytes, not str(#9428)

Fixes #9427

stdlib/zipimport.pyi

@@ -20,7 +20,7 @@ class zipimporter:
     def find_loader(self, fullname: str, path: str | None = ...) -> tuple[zipimporter | None, list[str]]: ...  # undocumented
     def find_module(self, fullname: str, path: str | None = ...) -> zipimporter | None: ...
     def get_code(self, fullname: str) -> CodeType: ...
-    def get_data(self, pathname: str) -> str: ...
+    def get_data(self, pathname: str) -> bytes: ...
     def get_filename(self, fullname: str) -> str: ...
     def get_resource_reader(self, fullname: str) -> ResourceReader | None: ...  # undocumented
     def get_source(self, fullname: str) -> str | None: ...