collapse nested namespaces

Author: Starlight220

wpilibNewCommands/src/main/native/include/frc2/command/CommandConcepts.h

@@ -8,11 +8,9 @@
 
 #include "frc2/command/CommandPtr.h"
 
-namespace frc2 {
-namespace cmd {
+namespace frc2::cmd {
 
 template <typename T>
 concept OwnedCommand = requires(T command) { CommandPtr(std::move(command)); };
 
-}  // namespace cmd
-}  // namespace frc2
+}  // namespace frc2::cmd