update coredns version and contributing.md as per 1.6

Signed-off-by: Anurag <contact.anurag7@gmail.com>

CONTRIBUTING.md

@@ -166,8 +166,9 @@ Cluster API maintains the most recent release/releases for all supported API and
 
 | Minor Release | API Version  | Supported Until                                     |
 |---------------|--------------|-----------------------------------------------------|
+| v1.6.x        | **v1beta1**  | when v1.8.0 will be released                        |
 | v1.5.x        | **v1beta1**  | when v1.7.0 will be released                        |
-| v1.4.x        | **v1beta1**  | when v1.6.0 will be released, tentatively Nov 2023  |
+| v1.4.x        | **v1beta1**  | EOL since 2023-12-05 - v1.6.0 release date          |
 | v1.3.x        | **v1beta1**  | EOL since 2023-07-25 - v1.5.0 release date          |
 | v1.2.x        | **v1beta1**  | EOL since 2023-03-28 - v1.4.0 release date          |
 | v1.1.x        | **v1beta1**  | EOL since 2022-07-18 - v1.2.0 release date (*)      |

docs/book/src/reference/versions.md

@@ -138,14 +138,9 @@ The Kubeadm Control Plane requires the Kubeadm Bootstrap Provider.
 
 | CAPI Version         | Max CoreDNS Version for Upgrade |
 |----------------------|---------------------------------|
-| >= v1.2.7 (v1beta1)  | v1.10.0                         |
-| >= v1.2.11 (v1beta1) | v1.10.1                         |
-| v1.3 (v1beta1)       | v1.10.0                         |
-| >= v1.3.4 (v1beta1)  | v1.10.1                         |
-| v1.4 (v1beta1)       | v1.10.1                         |
-| >= v1.4.6 (v1beta1)  | v1.11.1                         |
 | v1.5 (v1beta1)       | v1.10.1                         |
 | >= v1.5.1 (v1beta1)  | v1.11.1                         |
+| v1.6 (v1beta1)       | v1.11.1                         |
 
 #### Kubernetes version specific notes