SPARK-3955 part 2 [CORE] [HOTFIX] Different versions between jackson-mapper-asl and jackson-core-asl

pwendell https://github.com/apache/spark/commit/2483c1efb6429a7d8a20c96d18ce2fec93a1aff9 didn't actually add a reference to `jackson-core-asl` as intended, but a second redundant reference to `jackson-mapper-asl`, as markhamstra picked up on (https://github.com/apache/spark/pull/3716#issuecomment-68180192)  This just rectifies the typo. I missed it as well; the original PR https://github.com/apache/spark/pull/2818 had it correct and I also didn't see the problem.

Author: Sean Owen <sowen@cloudera.com>

Closes #3829 from srowen/SPARK-3955 and squashes the following commits:

6cfdc4e [Sean Owen] Actually refer to jackson-core-asl