Docs: fix a typo in transport client's put-mapping.asciidoc
It was talking about the wrong type.
@@ -60,7 +60,7 @@ You can use the same API to update an existing mapping:
[source,java]
--------------------------------------------------
client.admin().indices().preparePutMapping("twitter") <1>
- .setType("tweet") <2>
+ .setType("user") <2>
.setSource("{\n" + <3>
" \"properties\": {\n" +
" \"user_name\": {\n" +
