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/wpilib/fpga_time_conversion.h b/frc971/wpilib/fpga_time_conversion.h
index 51cc7a9..c279089 100644
--- a/frc971/wpilib/fpga_time_conversion.h
+++ b/frc971/wpilib/fpga_time_conversion.h
@@ -9,8 +9,7 @@
 #include "aos/time/time.h"
 #include "hal/cpp/fpga_clock.h"
 
-namespace frc971 {
-namespace wpilib {
+namespace frc971::wpilib {
 
 // Returns the offset from the monotonic clock to the FPGA time. This is defined
 // as `fpga_time - monotonic_time`.
@@ -51,7 +50,6 @@
   std::chrono::nanoseconds offset_ = std::chrono::nanoseconds::min();
 };
 
-}  // namespace wpilib
-}  // namespace frc971
+}  // namespace frc971::wpilib
 
 #endif  // FRC971_WPILIB_FPGA_TIME_CONVERSION_H_