refactor: Remove self class from scope

This will remove "Foo = serde_scope.types["Foo"]" from
the function generated for Foo.

```
def from_dict(data, reuse_instances=True):
    if reuse_instances is Ellipsis:
        reuse_instances = True

    Foo = serde_scope.types["Foo"]
    ...
```

Author: yukinarit

serde/de.py

@@ -122,6 +122,9 @@ def wrap(cls: Type):
 
         # Collect types used in the generated code.
         for typ in iter_types(cls):
+            if typ is cls:
+                continue
+
             if is_dataclass(typ) or is_enum(typ) or not is_primitive(typ):
                 scope.types[typ.__name__] = typ
 

serde/se.py

@@ -133,6 +133,9 @@ def wrap(cls: Type):
 
         # Collect types used in the generated code.
         for typ in iter_types(cls):
+            if typ is cls:
+                continue
+
             if is_dataclass(typ) or is_enum(typ) or not is_primitive(typ):
                 scope.types[typ.__name__] = typ