Nest some more namespaces

Did someone previously suggest that all namespace had been
nested?  Silly.

Signed-off-by: Stephan Pleines <pleines.stephan@gmail.com>
Change-Id: I22278c1caaeba8b47dc46fb2ed3078c20a11e190
diff --git a/frc971/vision/ceres/read_g2o.h b/frc971/vision/ceres/read_g2o.h
index 69fa16a..c427939 100644
--- a/frc971/vision/ceres/read_g2o.h
+++ b/frc971/vision/ceres/read_g2o.h
@@ -38,8 +38,7 @@
 
 #include "glog/logging.h"
 
-namespace ceres {
-namespace examples {
+namespace ceres::examples {
 
 // Reads a single pose from the input and inserts it into the map. Returns false
 // if there is a duplicate entry.
@@ -136,7 +135,6 @@
   return true;
 }
 
-}  // namespace examples
-}  // namespace ceres
+}  // namespace ceres::examples
 
 #endif  // EXAMPLES_CERES_READ_G2O_H_