don't use params.delete in ContextModulesController

refs CNVS-16685

Change-Id: I29e04e20eb243b14ed2246fe7c25a3e45185b1fb
Reviewed-on: https://gerrit.instructure.com/44291
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Rob Orton <rob@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>