docs: checkAuthMiddleware update

Author: igorlukanin

DEPRECATION.md

@@ -188,7 +188,7 @@ supports HTTP **and** WebSockets as transports, we want our authentication API
 to not rely on transport-specific details. We now recommend using
 [`checkAuth`][ref-checkauth] as a transport-agnostic method of authentication.
 This means the same authentication logic can be reused for both HTTP and
-Websockets transports.
+WebSockets transports.
 
 If you are using custom authorization, please take a [look at the
 documentation][link-custom-auth]

docs/pages/product/auth.mdx

@@ -233,14 +233,6 @@ Cube also allows you to provide your own JWT verification logic by setting a
 file. This function is expected to verify a JWT and return its claims as the
 security context.
 
-<WarningBox>
-
-Previous versions of Cube allowed setting a `checkAuthMiddleware()` parameter,
-which is now deprecated. We advise [migrating to a newer version of
-Cube][ref-config-migrate-cube].
-
-</WarningBox>
-
 As an example, if you needed to retrieve user information from an LDAP server,
 you might do the following: