Remove usage of CHECK_NOTNULL

We want to switch to absl logging instead of glog.  gtest and ceres are
going there, and we already have absl as a dependency.  ABSL doesn't
have CHECK_NOTNULL, and we can move things over in an easier to review
fashion.

Change-Id: Ifd9a11ec34a2357cec43f88dba015db9c28ed2cf
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/y2024/control_loops/superstructure/superstructure.cc b/y2024/control_loops/superstructure/superstructure.cc
index a485943..7f7da4f 100644
--- a/y2024/control_loops/superstructure/superstructure.cc
+++ b/y2024/control_loops/superstructure/superstructure.cc
@@ -36,7 +36,7 @@
     : frc971::controls::ControlLoop<Goal, Position, Status, Output>(event_loop,
                                                                     name),
       constants_fetcher_(event_loop),
-      robot_constants_(CHECK_NOTNULL(&constants_fetcher_.constants())),
+      robot_constants_(&constants_fetcher_.constants()),
       drivetrain_status_fetcher_(
           event_loop->MakeFetcher<frc971::control_loops::drivetrain::Status>(
               "/drivetrain")),