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/vision/intrinsics_calibration.cc b/frc971/vision/intrinsics_calibration.cc
index 452dd74..b4d3825 100644
--- a/frc971/vision/intrinsics_calibration.cc
+++ b/frc971/vision/intrinsics_calibration.cc
@@ -23,8 +23,7 @@
               "Intrinsics to use for estimating board pose prior to solving "
               "for the new intrinsics.");
 
-namespace frc971 {
-namespace vision {
+namespace frc971::vision {
 namespace {
 
 void Main() {
@@ -52,8 +51,7 @@
 }
 
 }  // namespace
-}  // namespace vision
-}  // namespace frc971
+}  // namespace frc971::vision
 
 int main(int argc, char **argv) {
   aos::InitGoogle(&argc, &argv);