cmctl: remove the word "legacy" for the kubectl plugin

Signed-off-by: Maël Valais <[email protected]>

Author: maelvls

content/docs/reference/cmctl.md

@@ -352,10 +352,8 @@ Resources](https://cert-manager.io/docs/releases/upgrading/remove-deprecated-api
 $ cmctl upgrade migrate-api-version --qps 5 --burst 10
 ```
 
-## Legacy kubectl plugin
+## Kubectl plugin
 
-We call the kubectl plugin "legacy" because we used to recommend using the standalone binary
-`cmctl` rather than the kubectl plugin because kubectl plugins used to not support auto-completion.
 Since kubectl 1.26, kubectl plugins support auto-completion, which means you will have the same
 experience with the standalone `cmctl` binary and with the kubectl plugin.