protobuf: fix stubtest errors (#8735)

Author: AlexWaygood

stubs/protobuf/@tests/stubtest_allowlist.txt

@@ -24,14 +24,11 @@ google.protobuf.text_format.MessageToBytes
 # a function. Typeshed's typing is more useful
 google.protobuf.service.Service.GetDescriptor
 
-# These are deliberately omitted in the stub
-# due to the fact that these classes have conflicting signatures for __init__/__new__.
+# These are deliberately omitted in the stub.
 # The classes also can't be constructed directly anyway,
 # so the signatures of their constructors are somewhat irrelevant.
 google.protobuf.descriptor.Descriptor.__init__
-google.protobuf.descriptor.Descriptor.__new__
 google.protobuf.descriptor.ServiceDescriptor.__init__
-google.protobuf.descriptor.ServiceDescriptor.__new__
 
 # Set to None at runtime - which doesn't match the Sequence base class.
 # It's a hack - just allow it.

stubs/protobuf/google/protobuf/reflection.pyi

@@ -1,6 +1,6 @@
 class GeneratedProtocolMessageType(type):
     def __new__(cls, name, bases, dictionary): ...
-    def __init__(self, name, bases, dictionary) -> None: ...
+    def __init__(cls, name, bases, dictionary) -> None: ...
 
 def ParseMessage(descriptor, byte_str): ...
 def MakeClass(descriptor): ...