Convert namedtuples to class syntax (#3321)

stdlib/3/os/__init__.pyi

@@ -393,7 +393,9 @@ if sys.platform != 'win32':
     def readv(fd: int, buffers: Sequence[bytearray]) -> int: ...
     def writev(fd: int, buffers: Sequence[bytes]) -> int: ...
 
-terminal_size = NamedTuple('terminal_size', [('columns', int), ('lines', int)])
+class terminal_size(NamedTuple):
+    columns: int
+    lines: int
 def get_terminal_size(fd: int = ...) -> terminal_size: ...
 
 def get_inheritable(fd: int) -> bool: ...