[build] Make Protobuf optional in CMake build (#7061)

wpimath/src/test/native/cpp/kinematics/proto/DifferentialDriveKinematicsProtoTest.cpp

@@ -2,10 +2,10 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
+#include <google/protobuf/arena.h>
 #include <gtest/gtest.h>
 
 #include "frc/kinematics/DifferentialDriveKinematics.h"
-#include "kinematics.pb.h"
 
 using namespace frc;