fix yard documentation for polling controllers

fixes CNVS-12913
YARD documentation needs to be above the explicit class it's referencing
and documenting.

Change-Id: I9e143c1f5300cad4abaa04f21c76820e8a0f6913
Reviewed-on: https://gerrit.instructure.com/34478
Reviewed-by: Derek DeVries <ddevries@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Josh Simpson <jsimpson@instructure.com>