Fix spelling error in Core App Quality docs.

Bug:
https://code.google.com/p/android/issues/detail?id=213248

Change-Id: Idf83eb4fdc09bc3c78a7786b4bf11707178092c7
(cherry picked from commit 08b10586120f3db6e29e5ece9c3e05462f0c01e9)
1 file changed