qt: Change transifex slug to new resource for 0.10.x

Make sure that translations are pulled from the 0.10.x resource
https://www.transifex.com/projects/p/bitcoin/resource/qt-translation-010x/

Closes bitcoin#4006.

.tx/config

@@ -1,7 +1,7 @@
 [main]
 host = https://www.transifex.com
 
-[bitcoin.tx]
+[bitcoin.qt-translation-010x]
 file_filter = src/qt/locale/bitcoin_<lang>.ts
 source_file = src/qt/locale/bitcoin_en.ts
 source_lang = en