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/y2023/localizer/localizer.cc b/y2023/localizer/localizer.cc
index 6f9a16b..a00ebe6 100644
--- a/y2023/localizer/localizer.cc
+++ b/y2023/localizer/localizer.cc
@@ -264,12 +264,12 @@
 
   switch (utils_.Alliance()) {
     case aos::Alliance::kRed:
-      ignore_tags =
-          CHECK_NOTNULL(constants_fetcher_.constants().ignore_targets()->red());
+      ignore_tags = constants_fetcher_.constants().ignore_targets()->red();
+      CHECK(ignore_tags != nullptr);
       break;
     case aos::Alliance::kBlue:
-      ignore_tags = CHECK_NOTNULL(
-          constants_fetcher_.constants().ignore_targets()->blue());
+      ignore_tags = constants_fetcher_.constants().ignore_targets()->blue();
+      CHECK(ignore_tags != nullptr);
       break;
     case aos::Alliance::kInvalid:
       return true;