add os.reload_environ (#14938)

Author: guoci

stdlib/os/__init__.pyi

@@ -729,6 +729,9 @@ environ: _Environ[str]
 if sys.platform != "win32":
     environb: _Environ[bytes]
 
+if sys.version_info >= (3, 14):
+    def reload_environ() -> None: ...
+
 if sys.version_info >= (3, 11) or sys.platform != "win32":
     EX_OK: Final[int]