Nest all namespaces

The compiler supports this now.  We can type less going forward.
No functional changes.

Signed-off-by: Stephan Pleines <pleines.stephan@gmail.com>
Change-Id: I29d6fa4f9aacc0e381f1a7637294db0392466995
diff --git a/frc971/zeroing/absolute_encoder_test.cc b/frc971/zeroing/absolute_encoder_test.cc
index 6e78faa..aa2fb9f 100644
--- a/frc971/zeroing/absolute_encoder_test.cc
+++ b/frc971/zeroing/absolute_encoder_test.cc
@@ -5,9 +5,7 @@
 
 #include "frc971/zeroing/zeroing_test.h"
 
-namespace frc971 {
-namespace zeroing {
-namespace testing {
+namespace frc971::zeroing::testing {
 
 using constants::AbsoluteEncoderZeroingConstants;
 
@@ -169,6 +167,4 @@
               ::testing::ElementsAre(ZeroingError::LOST_ABSOLUTE_ENCODER));
 }
 
-}  // namespace testing
-}  // namespace zeroing
-}  // namespace frc971
+}  // namespace frc971::zeroing::testing