mc_att_control: remove time constant parameter

Because the parameter does not make sense from a control theory
perspective. Either you have a gain with the unit 1/s or an inverse
gain or time constant with the unit s. But the time constant parameter
was neither bound to any exact unit nor did it apply instead of a gain.
Rather it adjusted multiple gains from rate and attitude control
according to an arbitrary scale. This can only by accident lead to
good tuning.

src/modules/mc_att_control/mc_att_control_params.c

@@ -39,34 +39,6 @@
  * @author Anton Babushkin <anton@px4.io>
  */
 
-/**
- * Roll time constant
- *
- * Reduce if the system is too twitchy, increase if the response is too slow and sluggish.
- *
- * @unit s
- * @min 0.15
- * @max 0.25
- * @decimal 2
- * @increment 0.01
- * @group Multicopter Attitude Control
- */
-PARAM_DEFINE_FLOAT(MC_ROLL_TC, 0.2f);
-
-/**
- * Pitch time constant
- *
- * Reduce if the system is too twitchy, increase if the response is too slow and sluggish.
- *
- * @unit s
- * @min 0.15
- * @max 0.25
- * @decimal 2
- * @increment 0.01
- * @group Multicopter Attitude Control
- */
-PARAM_DEFINE_FLOAT(MC_PITCH_TC, 0.2f);
-
 /**
  * Roll P gain
  *