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/joystick_reader.cc b/y2024/joystick_reader.cc
index 711f9d2..88bf441 100644
--- a/y2024/joystick_reader.cc
+++ b/y2024/joystick_reader.cc
@@ -82,7 +82,9 @@
         superstructure_status_fetcher_(
             event_loop->MakeFetcher<control_loops::superstructure::Status>(
                 "/superstructure")),
-        robot_constants_(CHECK_NOTNULL(robot_constants)) {}
+        robot_constants_(robot_constants) {
+    CHECK(robot_constants_ != nullptr);
+  }
 
   void AutoEnded() override { AOS_LOG(INFO, "Auto ended.\n"); }