Tighten length limit for channel names according to RFC 1459

http2irc.py

@@ -142,7 +142,7 @@ class Config(dict):
 					raise InvalidConfig(f'Invalid map {key!r} IRC channel: does not start with # or &')
 				if any(x in map_['ircchannel'][1:] for x in (' ', '\x00', '\x07', '\r', '\n', ',')):
 					raise InvalidConfig(f'Invalid map {key!r} IRC channel: contains forbidden characters')
-				if 14 + len(map_['ircchannel']) > 510: # 14 = prefix 'PRIVMSG ' + suffix ' :' + at least one UTF-8 character; implicitly also covers the shorter JOIN/PART messages
+				if len(map_['ircchannel']) > 200:
 					raise InvalidConfig(f'Invalid map {key!r} IRC channel: too long')
 
 				if 'auth' in map_: