build(helm): update cert-manager to v1.21.0

Author: renovate-bot

apps/versions.toml

@@ -21,7 +21,7 @@ helm = "https://argoproj.github.io/argo-helm"
 chart = "argo-events"
 
 [cert-manager]
-version = "v1.20.2"
+version = "v1.21.0"
 helm = "https://charts.jetstack.io"
 
 [cilium]