qapi: fix example of dump-guest-memory

Example output lacks mandatory member @paging.  Provide it.
Signed-off-by: NVictor Toso <victortoso@redhat.com>
Reviewed-by: NJohn Snow <jsnow@redhat.com>
Message-Id: <20220328140604.41484-15-victortoso@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

qapi/dump.json

@@ -83,7 +83,7 @@
 # Example:
 #
 # -> { "execute": "dump-guest-memory",
-#      "arguments": { "protocol": "fd:dump" } }
+#      "arguments": { "paging": false, "protocol": "fd:dump" } }
 # <- { "return": {} }
 #
 ##