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/extrinsics_calibration.h b/frc971/vision/extrinsics_calibration.h
index f6c3ccc..97d719f 100644
--- a/frc971/vision/extrinsics_calibration.h
+++ b/frc971/vision/extrinsics_calibration.h
@@ -6,8 +6,7 @@
 
 #include "frc971/vision/calibration_accumulator.h"
 
-namespace frc971 {
-namespace vision {
+namespace frc971::vision {
 
 struct CalibrationParameters {
   Eigen::Quaternion<double> initial_orientation =
@@ -55,7 +54,6 @@
 void Visualize(const CalibrationData &data,
                const CalibrationParameters &calibration_parameters);
 
-}  // namespace vision
-}  // namespace frc971
+}  // namespace frc971::vision
 
 #endif  // FRC971_VISION_EXTRINSICS_CALIBRATION_H_