Correction of value of description in bn-probhat.js to "Bengali" from "Assamese"

Addressed issue posted at https://github.com/wikimedia/jquery.ime/issues/367

2014-08-23 : Indranil Das Gupta <indradg@gmail.com> / L2C2 Techologies
Merge pull request #368 from l2c2technologies/master

Correction of value of description in bn-probhat.js to "Bengali" from "Assamese"