fix wording on @deprecated

Author: yoshuawuyts

design/mvp/WIT.md

@@ -958,10 +958,9 @@ change type or be removed at any time. An important expectation set by the
 default unless explicitly opted-into by the developer.
 
 Finally, the `@deprecated` gate on `e` indicates that `e` should no longer be
-used starting version `0.2.1`. Both toolchains and host runtimes may
-warn users if they detect an `@deprecated` API is being used. An `@deprecated`
-gate is required to always be paired up with an `@since` gate. It is
-semantically invalid to use `@deprecated` without also using `@since`.
+used starting version `0.2.1`. Both toolchains and host runtimes may warn users
+if they detect an `@deprecated` API is being used. An `@deprecated` gate is
+required to always be paired up with either a `@since` or `@deprecated` gate.
 
 Together, these gates support a development flow in which new features start
 with an `@unstable` gate while the details are still being hashed out. Then,