docs/proposal: drop broken link to ClusterClass google doc

Signed-off-by: Stefan Büringer [email protected]

Author: sbueringer

docs/proposals/20210526-cluster-class-and-managed-topologies.md

@@ -599,7 +599,7 @@ The initial plan is to rollout Cluster Class and support for managed topologies
 
 - 04/05/2021: Proposed idea in an [issue](https://github.com/kubernetes-sigs/cluster-api/issues/4430)
 - 05/05/2021: Compile a [Google Doc](https://docs.google.com/document/d/1lwxgBK3Q7zmNkOSFqzTGmrSys_vinkwubwgoyqSRAbI/edit#) following the CAEP template
-- 05/19/2021: Present proposal at a [community meeting](https://docs.google.com/document/d/1LdooNTbb9PZMFWy3_F-XAsl7Og5F2lvG3tCgQvoB5e4/edit#heading=h.bz527cpoqorn)
+- 05/19/2021: Present proposal at a community meeting
 - 05/26/2021: Open proposal PR
 - 07/21/2021: First version of the proposal merged
 - 10/04/2021: Added support for patches and variables