Remove duplicated help messages from `workspace --help`

Fixes #17165

command/workspace_command.go

@@ -35,14 +35,6 @@ Usage: terraform workspace
 
   Create, change and delete Terraform workspaces.
 
-
-Subcommands:
-
-    show      Show the current workspace name.
-    list      List workspaces.
-    select    Select a workspace.
-    new       Create a new workspace.
-    delete    Delete an existing workspace.
 `
 	return strings.TrimSpace(helpText)
 }