docs: add node meta command docs (#16828)

* docs: add node meta command docs

Fixes #16758

* it helps if you actually add the files to git

* fix typos and examples vs usage

command/node_meta_apply.go

@@ -37,10 +37,10 @@ Node Meta Apply Options:
     the request will be used by default.
 
   -unset key1,...,keyN
-    Unset the command separated list of keys.
+    Unset the comma separated list of keys.
 
-    Example:
-      $ nomad node meta apply -unset testing,tempvar ready=1 role=preinit-db
+  Example:
+    $ nomad node meta apply -unset testing,tempvar ready=1 role=preinit-db
 `
 	return strings.TrimSpace(helpText)
 }