Don't disable drivetrain outputs on missing IMU

This also makes it so that the down-estimator doesn't assume that the
2024 robot exists in simulation....

Change-Id: I308f3d88fc0956766a5d46c7438331aeec00b754
Signed-off-by: James Kuszmaul <jabukuszmaul+collab@gmail.com>
diff --git a/frc971/control_loops/drivetrain/drivetrain.cc b/frc971/control_loops/drivetrain/drivetrain.cc
index 81f1d8d..242495f 100644
--- a/frc971/control_loops/drivetrain/drivetrain.cc
+++ b/frc971/control_loops/drivetrain/drivetrain.cc
@@ -579,9 +579,7 @@
 
   // If the filters aren't ready/valid, then disable all outputs (currently,
   // this only happens if the IMU is faulted or has not zeroed).
-  // TODO(james): Add exceptions so that during competitive play the driver
-  // can retain minimal control of the robot.
-  if (!filters_.Ready()) {
+  if (dt_config_.require_imu_for_output && !filters_.Ready()) {
     output_struct.left_voltage = 0.0;
     output_struct.right_voltage = 0.0;
   }