Update cert-manager chart to prepare for k8s version 1.20 support

Problem to solve

The current version of certmanager chart this Cluster Management template project is using is not supported on Kubernetes v 1.20 clusters. More details on this issue

Although we don't yet officially support integration with 1.20 k8s version we should track this limitation to get ready for when we add support.

Proposal

1. Update the main certmanager release to whatever is the latest version of cert-manager
2. Remove the crds-chart in favor of setting installCRDs to true (see docs)
3. Update the issuer-chart to use the new CRDs

For discussion

Considering that users may not migrate to a cluster management project until several milestones into the 14.x series of GitLab, when is it safe to start upgrading the default versions in here?

• Should we create a separate project template just for users migrating over?
• Or should we keep a cert-manager-legacy folder for users migrating over from releases previously managed by GitLab?