Update db.models.functions.comparison (#206)

Adds the missing functions [`Collate`](https://docs.djangoproject.com/en/4.2/ref/models/database-functions/#collate) and [`JSONObject`](https://docs.djangoproject.com/en/4.2/ref/models/database-functions/#jsonobject) to `db.models.functions.comparison`.

Also makes them available from `db.models.functions`.

django-stubs/db/models/functions/__init__.pyi

@@ -1,6 +1,8 @@
 from .comparison import Cast as Cast
 from .comparison import Coalesce as Coalesce
+from .comparison import Collate as Collate
 from .comparison import Greatest as Greatest
+from .comparison import JSONObject as JSONObject
 from .comparison import Least as Least
 from .comparison import NullIf as NullIf
 from .datetime import Extract as Extract

django-stubs/db/models/functions/comparison.pyi

@@ -9,6 +9,12 @@ class Cast(Func):
     ) -> None: ...
 
 class Coalesce(Func): ...
+class Collate(Func):
+    def __init__(self, expression: Any, collation: str) -> None: ...
+
 class Greatest(Func): ...
+class JSONObject(Func):
+    def __init__(self, **fields: Any) -> None: ...
+
 class Least(Func): ...
 class NullIf(Func): ...