Drop release-0.3 from book docs (#1373)

Signed-off-by: Prajyot-Parab <[email protected]>
Co-authored-by: Prajyot-Parab <[email protected]>

Author: k8s-infra-cherrypick-robot

docs/book/src/introduction.md

@@ -24,7 +24,6 @@ This book documents Cluster API Provider IBM Cloud v0.5. For other versions plea
 * [main.cluster-api-ibmcloud.sigs.k8s.io](https://main.cluster-api-ibmcloud.sigs.k8s.io)
 * [release-0-5.cluster-api-ibmcloud.sigs.k8s.io](https://release-0-5.cluster-api-ibmcloud.sigs.k8s.io/)
 * [release-0-4.cluster-api-ibmcloud.sigs.k8s.io](https://release-0-4.cluster-api-ibmcloud.sigs.k8s.io/)
-* [release-0-3.cluster-api-ibmcloud.sigs.k8s.io](https://release-0-3.cluster-api-ibmcloud.sigs.k8s.io/)
 
 </aside>