remove 802.11b support and htmode

The htmode option has been dropped, the channel width is now always set to 20MHz (https://github.com/freifunk-gluon/gluon/issues/487).

site.conf

@@ -16,7 +16,9 @@
 
     wifi24 = {
         channel = 1,
-        htmode = 'HT20', --only for optic 
+        --disables 802.11b rates
+        supported_rates = {6000, 9000, 12000, 18000, 24000, 36000, 48000, 54000},
+        basic_rate = {6000, 9000, 18000, 36000, 54000},
         ap = {
             ssid = 'Freifunk',
         },
@@ -29,7 +31,6 @@
 
     wifi5 = {
         channel = 44,
-        htmode = 'HT20', --only for optic
         ap = {
             ssid = 'Freifunk',
         },