Drop info about very stale releases

Those old releases are definitely out of support.

Author: lmktfy

content/en/docs/reference/access-authn-authz/authentication.md

@@ -1065,10 +1065,6 @@ extra:
   - profile
 ```
 
-{{< note >}}
-Prior to Kubernetes 1.11.3 (and 1.10.7, 1.9.11), the `extra` key could only contain characters that
-were [legal in HTTP header labels](https://tools.ietf.org/html/rfc7230#section-3.2.6).
-{{< /note >}}
 
 #### Client certificate {#reverse-proxy-client-certificate}