[commands] Delete UB-causing rvalue variants of CommandPtr methods (#4923)

Co-authored-by: Ryan Blue <ryanzblue@gmail.com>

wpilibNewCommands/src/main/native/cpp/frc2/command/CommandScheduler.cpp

@@ -433,9 +433,10 @@ void CommandScheduler::OnCommandFinish(Action action) {
 
 void CommandScheduler::RequireUngrouped(const Command* command) {
   if (command->IsComposed()) {
-    throw FRC_MakeError(
-        frc::err::CommandIllegalUse,
-        "Commands cannot be added to more than one CommandGroup");
+    throw FRC_MakeError(frc::err::CommandIllegalUse,
+                        "Commands that have been composed may not be added to "
+                        "another composition or scheduled "
+                        "individually!");
   }
 }