Take into account that flags:# could be not always the first argument

For instance, in Layer 91, Poll's flags:# is at the second position.
This mess also happened in the past (thanks tg devs) and eventually will
be fixed again with the next Layer update, but from now on Pyrogram
will be able to correctly generate code even in such cases.

compiler/api/template/mtproto.txt

@@ -16,7 +16,6 @@ class {class_name}(Object):
 
     @staticmethod
     def read(b: BytesIO, *args) -> "{class_name}":
-        {read_flags}
         {read_types}
         return {class_name}({return_arguments})
 
@@ -24,6 +23,5 @@ class {class_name}(Object):
         b = BytesIO()
         b.write(Int(self.ID, False))
 
-        {write_flags}
         {write_types}
         return b.getvalue()