constify and deautoify more things in vision

This was part of my effort to understand how things work.

Change-Id: I49dae7400fba8ec1f02d006f3d14c6dc254a8187
diff --git a/y2019/vision/target_finder.cc b/y2019/vision/target_finder.cc
index d39764a..45678eb 100644
--- a/y2019/vision/target_finder.cc
+++ b/y2019/vision/target_finder.cc
@@ -7,7 +7,7 @@
 namespace y2019 {
 namespace vision {
 
-TargetFinder::TargetFinder() { target_template_ = Target::MakeTemplate(); }
+TargetFinder::TargetFinder() : target_template_(Target::MakeTemplate()) {}
 
 aos::vision::RangeImage TargetFinder::Threshold(aos::vision::ImagePtr image) {
   const uint8_t threshold_value = GetThresholdValue();