Revert "spec: selenium 2.40 firefox 2.70 upgrades"

This reverts commit de462a82d2682f8d70cce4f54f72e88523c9e461.

Change-Id: I70f6ae29a4e8955b84d2be03672b3a7c9c1a6bd3
Reviewed-on: https://gerrit.instructure.com/32575
Reviewed-by: Shawn Meredith <shawn@instructure.com>
Product-Review: Shawn Meredith <shawn@instructure.com>
QA-Review: Shawn Meredith <shawn@instructure.com>
Tested-by: Shawn Meredith <shawn@instructure.com>