Merge pull request #8150 from k8s-infra-cherrypick-robot/cherry-pick-8117-to-release-1.3

[release-1.3] 📖 docs: document plan to remove v1alpha3 and v1alpha4 apiVersions

Author: k8s-ci-robot

CONTRIBUTING.md

@@ -139,11 +139,11 @@ Cluster API maintains the most recent release/releases for all supported API and
 - The API version is determined from the GroupVersion defined in the top-level `api/` package.
 - The EOL date of each API Version is determined from the last release available once a new API version is published.
 
-| API Version  | Supported Until      |
-|--------------|----------------------|
-| **v1beta1**  | TBD (current stable) |
-| **v1alpha4** | EOL since 2022-04-06 |
-| **v1alpha3** | EOL since 2022-02-23 |
+| API Version  | Supported Until                                                                         |
+|--------------|-----------------------------------------------------------------------------------------|
+| **v1beta1**  | TBD (current stable)                                                                    |
+| **v1alpha4** | EOL since 2022-04-06 ([apiVersion removal](#removal-of-v1alpha3--v1alpha4-apiversions)) |
+| **v1alpha3** | EOL since 2022-02-23 ([apiVersion removal](#removal-of-v1alpha3--v1alpha4-apiversions)) |
 
 - For the latest API version we support the two most recent minor releases; older minor releases are immediately unsupported when a new major/minor release is available. 
 - For older API versions we only support the most recent minor release until the API version reaches EOL.
@@ -161,6 +161,18 @@ Cluster API maintains the most recent release/releases for all supported API and
 
 - Exceptions can be filed with maintainers and taken into consideration on a case-by-case basis.
 
+### Removal of v1alpha3 & v1alpha4 apiVersions
+
+We are going to remove the apiVersions in upcoming releases:
+* v1.5:
+  * Kubernetes API server will stop serving the v1alpha3 apiVersion
+* v1.6:
+  * v1alpha3 apiVersion will be removed from the CRDs
+  * Kubernetes API server will stop serving the v1alpha4 apiVersion
+* v1.7
+  * v1alpha4 apiVersion will be removed from the CRDs
+For more details and latest information please see the following issue: [Removing v1alpha3 & v1alpha4 apiVersions](https://github.com/kubernetes-sigs/cluster-api/issues/8038).
+
 ## Contributing a Patch
 
 1. If you haven't already done so, sign a Contributor License Agreement (see details above).