Convert namedtuples to class syntax (#3321)

stdlib/2and3/dis.pyi

@@ -21,19 +21,15 @@ _have_code_or_string = Union[_have_code, str, bytes]
 
 
 if sys.version_info >= (3, 4):
-    Instruction = NamedTuple(
-        "Instruction",
-        [
-            ('opname', str),
-            ('opcode', int),
-            ('arg', Optional[int]),
-            ('argval', Any),
-            ('argrepr', str),
-            ('offset', int),
-            ('starts_line', Optional[int]),
-            ('is_jump_target', bool)
-        ]
-    )
+    class Instruction(NamedTuple):
+        opname: str
+        opcode: int
+        arg: Optional[int]
+        argval: Any
+        argrepr: str
+        offset: int
+        starts_line: Optional[int]
+        is_jump_target: bool
 
     class Bytecode:
         codeobj: types.CodeType