Assuming the bed heater is heater zero, If you change the M116 line to be:
if heat.heaters[0].current < 60
M116
it will only do the M116 if the current temperature is less than 60.
Note that the M116 needs to be indented by some spaces (I use four), and the next line must not be indented - RRF uses indents to delimit loops, conditional blocks etc.
I'd actually be inclined to make it
if heat.heaters[0].current < heat.heaters[0].standby
M116
then it will do the M116 if the current temperature is less than whatever the heater is set to (as standby), so if you change the '60' value in future it will not need changing in multiple places in the file.