Change the safe edns-udp-size from 1400 to 1432
When backporting the Don't Fragment UDP socket option, it was noticed that the edns-udp-size probing uses 1432 as one of the values to be probed and the documentation would be recommending 1400 as the safe value. As the safe value can be from the 1400-1500 interval, the documentation has been changed to match the probed value, so we do not skip it.
Closes #2183 (closed)