Fix version argument (#17739)

Co-authored-by: Violet Hynes <violet.hynes@hashicorp.com>

website/content/docs/commands/plugin/register.mdx

@@ -52,6 +52,6 @@ flags](/vault/docs/commands) included on all commands.
 - `-command` `(string: "")` - Name of the command to run to invoke the binary.
   By default, this is the name of the plugin.
 
-- `-plugin-version` `(string: "")` - Semantic version of the plugin to run from
+- `-version` `(string: "")` - Semantic version of the plugin to run from
   the catalog. If unspecified, refers to the unversioned plugin registered with
   the same name and type, or the built-in plugin, in that order of precedence.