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/zeroing/zeroing_test.h b/frc971/zeroing/zeroing_test.h
index cadbe6c..497f833 100644
--- a/frc971/zeroing/zeroing_test.h
+++ b/frc971/zeroing/zeroing_test.h
@@ -4,9 +4,7 @@
 #include "frc971/control_loops/position_sensor_sim.h"
 #include "frc971/zeroing/zeroing.h"
 
-namespace frc971 {
-namespace zeroing {
-namespace testing {
+namespace frc971::zeroing::testing {
 
 using control_loops::PositionSensorSimulator;
 using FBB = flatbuffers::FlatBufferBuilder;
@@ -27,6 +25,4 @@
   }
 };
 
-}  // namespace testing
-}  // namespace zeroing
-}  // namespace frc971
+}  // namespace frc971::zeroing::testing