Fix build issue

Signed-off-by: Roman Kazantsev <roman.kazantsev@intel.com>

inference-engine/src/mkldnn_plugin/nodes/mkldnn_detection_output_node.cpp

@@ -112,7 +112,6 @@ void MKLDNNDetectionOutputNode::prepareParams() {
         << priorsNum * locNumForClasses * 4 << " vs "
         << idLocDims[1] << ")";
 
-    const auto& idConfDims = getParentEdgeAt(ID_CONF)->getMemory().GetShape().getStaticDims();
     if (priorsNum * classesNum != static_cast<int>(idConfDims.back()))
         IE_THROW() << errorPrefix << "has incorrect number of priors, which must match number of confidence predictions.";