Update RELEASE.md

RELEASE.md

@@ -1,21 +1,7 @@
 Release type: minor
 
-The common `node: Node` used to resolve relay nodes means we will be relying on
-is_type_of to check if the returned object is in fact a subclass of the Node
-interface.
+This release introduces `strawberry.cast`, which can be used when returning
+a non Strawberry type to tell Strawberry what GraphQL type you wanted to return.
 
-However, integrations such as Django, SQLAlchemy and Pydantic will not return
-the type itself, but instead an alike object that is later resolved to the
-expected type.
-
-In case there are more than one possible type defined for that model that is
-being returned, the first one that replies True to `is_type_of` check would be
-used in the resolution, meaning that when asking for `"PublicUser:123"`,
-strawberry could end up returning `"User:123"`, which can lead to security
-issues (such as data leakage).
-
-In here we are introducing a new `strawberry.cast`, which will be used to mark
-an object with the already known type by us, and when asking for is_type_of that
-mark will be used to check instead, ensuring we will return the correct type.
-
-That `cast` is already in place for the relay node resolution and pydantic.
+This is mostly useful when using unions or interfaces and returning non Strawberry 
+types, like in integration like Strawberry Django, SQLAlchemy and Pydantic.