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/aos/events/logging/logfile_utils.cc b/aos/events/logging/logfile_utils.cc
index 30ed3d7..0d10a99 100644
--- a/aos/events/logging/logfile_utils.cc
+++ b/aos/events/logging/logfile_utils.cc
@@ -2442,7 +2442,7 @@
 
 Message TimestampMapper::MatchingMessageFor(const Message &message) {
   // Figure out what queue index we are looking for.
-  CHECK_NOTNULL(message.header);
+  CHECK(message.header != nullptr);
   CHECK(message.header->remote_queue_index.has_value());
   const BootQueueIndex remote_queue_index =
       BootQueueIndex{.boot = message.monotonic_remote_boot,