Fix internal deprecation warnings (#4257)

This allows us to error out on deprecation warnings for thirdparty
libraries and standard library features.

Co-authored-by: Starlight220 <53231611+Starlight220@users.noreply.github.com>

wpilibNewCommands/src/main/java/edu/wpi/first/wpilibj2/command/Command.java

@@ -254,6 +254,7 @@ public interface Command {
    * @return the decorated command
    * @deprecated use {@link #endlessly()} instead.
    */
+  @SuppressWarnings("removal") // PerpetualCommand
   @Deprecated(forRemoval = true, since = "2023")
   default PerpetualCommand perpetually() {
     return new PerpetualCommand(this);

wpilibNewCommands/src/main/java/edu/wpi/first/wpilibj2/command/PerpetualCommand.java

@@ -56,6 +56,7 @@ public class PerpetualCommand extends CommandBase {
     return m_command.runsWhenDisabled();
   }
 
+  @SuppressWarnings("removal") // Command.perpetually()
   @Override
   public PerpetualCommand perpetually() {
     return this;