config: Remove hold_current from sample configs and sample macros

Now that the documentation recommends that hold_current not be set,
update the example config files to not specify a hold_current.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

config/generic-bigtreetech-e3-rrf-v1.1.cfg

@@ -23,7 +23,6 @@ homing_speed: 50
 [tmc2209 stepper_x]
 uart_pin: PD6
 run_current: 0.580
-hold_current: 0.500
 stealthchop_threshold: 999999
 
 [stepper_y]
@@ -40,7 +39,6 @@ homing_speed: 50
 [tmc2209 stepper_y]
 uart_pin: PD1
 run_current: 0.580
-hold_current: 0.500
 stealthchop_threshold: 999999
 
 [stepper_z]
@@ -56,7 +54,6 @@ position_max: 250
 [tmc2209 stepper_z]
 uart_pin: PD15
 run_current: 0.580
-hold_current: 0.500
 stealthchop_threshold: 999999
 
 [extruder]
@@ -80,7 +77,6 @@ max_temp: 250
 [tmc2209 extruder]
 uart_pin: PD11
 run_current: 0.650
-hold_current: 0.500
 stealthchop_threshold: 999999
 
 [heater_bed]