Pontoon: Update Bengali (bn-IN) localization of Pontoon Intro
Pontoon: Update Bengali (bn-IN) localization of Pontoon Intro

Localization authors:
- Abhyudaya Chatterjee <chatterjeeabhyudaya@gmail.com>
- Sayantan Saha <sayantanmozillian@gmail.com>
- Ayan Choudhury <ping2ayan@gmail.com>
- Swarnava Sengupta <swarnavasengupta@gmail.com>
- Mainak <rcmainak24@gmail.com>
- Suryadip Basu <suryadip.basu@yahoo.com>
- Shiladittya Paul <shiladittyapaul@gmail.com>

jotes/pontoon-intro,jotes/pontoon-intro,jotes/pontoon-intro