qmp-commands: move 'query-iothreads' doc to schema

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

docs/qmp-commands.txt

@@ -1945,36 +1945,6 @@ Example:
       ]
    }
 
-query-iothreads
----------------
-
-Returns a list of information about each iothread.
-
-Note this list excludes the QEMU main loop thread, which is not declared
-using the -object iothread command-line option.  It is always the main thread
-of the process.
-
-Return a json-array. Each iothread is represented by a json-object, which contains:
-
-- "id": name of iothread (json-str)
-- "thread-id": ID of the underlying host thread (json-int)
-
-Example:
-
--> { "execute": "query-iothreads" }
-<- {
-      "return":[
-         {
-            "id":"iothread0",
-            "thread-id":3134
-         },
-         {
-            "id":"iothread1",
-            "thread-id":3135
-         }
-      ]
-   }
-
 query-pci
 ---------