Fix runway ref example

The 'Runway number' field which is displayed in the simple view when editing a way tagged as 'aeroway=runway' gives an example of '01-36' - this is an invalid combination and may lead to confusion. This should instead be either '18-36' or '01-19'

This patch changes the example to read '18-36'

Runways have a 2-digit number at each end indicating which direction they point (in tens-of-degrees). Each number is 180 degrees +/- the other. For example, a runway that is oriented north/south will have 36 at the southern end and 18 at the northern end. A pilot may say 'landing on runway 18' - this means he intends to land his aircraft facing due south.