stubtest: minor cleanup now 3.6 is no longer supported (#13292)

mypy/stubtest.py

@@ -302,12 +302,6 @@ def _belongs_to_runtime(r: types.ModuleType, attr: str) -> bool:
         yield from verify(stub_entry, runtime_entry, object_path + [entry])
 
 
-if sys.version_info >= (3, 7):
-    _WrapperDescriptorType = types.WrapperDescriptorType
-else:
-    _WrapperDescriptorType = type(object.__init__)
-
-
 @verify.register(nodes.TypeInfo)
 def verify_typeinfo(
     stub: nodes.TypeInfo, runtime: MaybeMissing[Type[Any]], object_path: List[str]
@@ -378,7 +372,7 @@ class SubClass(runtime):  # type: ignore
         # The vast majority of these are false positives.
         if not (
             isinstance(stub_to_verify, Missing)
-            and isinstance(runtime_attr, _WrapperDescriptorType)
+            and isinstance(runtime_attr, types.WrapperDescriptorType)
             and is_dunder(mangled_entry, exclude_special=True)
         ):
             yield from verify(stub_to_verify, runtime_attr, object_path + [entry])

mypy/test/teststubtest.py

@@ -1195,8 +1195,6 @@ class _Options(TypedDict):
 
     @collect_cases
     def test_protocol(self) -> Iterator[Case]:
-        if sys.version_info < (3, 7):
-            return
         yield Case(
             stub="""
             from typing_extensions import Protocol