IMapper: change an error message

Change the error message that prints when IMapper 3.0 isn't present.
The old warning was causing unnecessary concerns.

Bug: 128013727
Test: compile
Change-Id: I197cd953d08a8e9f3bdee92cede973bf1b97dfe2
(cherry picked from commit ccbd24f6336bf7141b9a6e463b89aa027b289bfe)
1 file changed