[kn-plugin-workflow] Fix undeploy --help returning deploy command help text

[domhanak]

Goal
Remove deploy mentions from undeploy --help command

Actual results

	

Usage:
  kn workflow undeploy [flags]

Examples:

	# Undeploy the workflow project from the current directory's project. 
	# You must provide target namespace.
	kn workflow undeploy --namespace <your_namespace>

	# Persist the generated Kubernetes manifests on a given path and deploy the 
	# workflow from the current directory's project. 
	kn workflow undeploy --custom-generated-manifests-dir=<full_directory_path>

	# Specify a custom manifest files directory.
	# This option *will not* automatically generate the manifest files, but will use the existing ones.
	kn workflow deploy --custom-manifests-dir=<full_directory_path>

	# Specify a custom subflows files directory. (default: ./subflows)
	kn workflow deploy --subflows-dir=<full_directory_path>

	# Specify a custom support specs directory. (default: ./specs)
	kn workflow deploy --specs-dir=<full_directory_path>

	# Specify a custom support schemas directory. (default: ./schemas)
	kn workflow deploy --schemas-dir=<full_directory_path>

       ...

Expected results

	Undeploy a SonataFlow project in Kubernetes via the SonataFlow Operator. 
	

Usage:
  kn workflow undeploy [flags]

Examples:

	# Undeploy the workflow project from the current directory's project. 
	# You must provide target namespace.
	kn workflow undeploy --namespace <your_namespace>
        ...