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/y2019/jevois/spi.cc b/y2019/jevois/spi.cc
index b3b6550..85ad988 100644
--- a/y2019/jevois/spi.cc
+++ b/y2019/jevois/spi.cc
@@ -39,8 +39,7 @@
 //   Note that empty frames are still sent to indicate that the camera is
 //   still working even though it doesn't see any targets.
 
-namespace frc971 {
-namespace jevois {
+namespace frc971::jevois {
 namespace {
 
 constexpr float heading_min() { return -3; }
@@ -312,5 +311,4 @@
   return message;
 }
 
-}  // namespace jevois
-}  // namespace frc971
+}  // namespace frc971::jevois