Update books/02_Exodus.tex

In Exo 6:12, added a missing period at end of sentence (and just before close quote mark).

In Exo 9:22, added a missing close quote mark at the end of verse 22.

In Exo 11:9, added a missing close quote mark at the end of verse 9.

Amended by Charles Welty. Authorized by William P. Welty of The ISV Foundation on 06 JAN 2013 at 9:06AM PST.