wireless-regdb: update to wireless-regdb-2020.04.29

[MilhouseVH]

wireless-regdb: update regulatory database based on preceding changes
wireless-regdb: update rules for US on 2.4/5G
GB: Extend to cover DMG channels 5 & 6
wireless-regdb: Update regulatory rules for Singapore (SG)
wireless-regdb: Update regulatory rules for Indonesia (ID)
regdb: fix compatibility with python2
wireless-regdb: Update regulatory rules for Russia (RU)
wireless-regdb: Harmonize ranges of CEPT countries (stand of July 2019)
wireless-regdb: Fix ranges of EU countries as they are harmonized since 2014
wireless-regdb: Extend 5470-5725 MHz range to 5730 MHz for Taiwan (TW)
wireless-regdb: Fix overlapping ranges for Switzerland and Liechtenstein

[chewitt]

Can you backport to 9.2 as well please, if not already in a backports bundle PR.