Fix typo in invoice factory.
Fix typo in invoice factory.

huerlisi/bookyt,wtag/bookyt,gaapt/bookyt,huerlisi/bookyt,hauledev/bookyt,silvermind/bookyt,huerlisi/bookyt,hauledev/bookyt,gaapt/bookyt,wtag/bookyt,xuewenfei/bookyt,gaapt/bookyt,xuewenfei/bookyt,hauledev/bookyt,gaapt/bookyt,wtag/bookyt,silvermind/bookyt,silvermind/bookyt,silvermind/bookyt,xuewenfei/bookyt,hauledev/bookyt