clang-tidy: modernize-use-override (NFC)

Add NOLINT to CommandTestBase due to gmock not adding "override" keyword,
which causes warnings on clang.

Author: PeterJohnson

include/frc2/command/Command.h

@@ -49,7 +49,7 @@ class ProxyScheduleCommand;
 class Command : public frc::ErrorBase {
  public:
   Command() = default;
-  virtual ~Command();
+  ~Command() override;
 
   Command(const Command&);
   Command& operator=(const Command&);

include/frc2/command/CommandScheduler.h

@@ -39,7 +39,7 @@ class CommandScheduler final : public frc::Sendable,
    */
   static CommandScheduler& GetInstance();
 
-  ~CommandScheduler();
+  ~CommandScheduler() override;
   CommandScheduler(const CommandScheduler&) = delete;
   CommandScheduler& operator=(const CommandScheduler&) = delete;
 

include/frc2/command/RunCommand.h

@@ -45,7 +45,7 @@ class RunCommand : public CommandHelper<CommandBase, RunCommand> {
 
   RunCommand(const RunCommand& other) = default;
 
-  void Execute();
+  void Execute() override;
 
  protected:
   std::function<void()> m_toRun;