netflow padding max bound

spec 254 says Max must not be lower than ito_low_ms,

http://eweiibe6tdjsdprb4px6rqrzzcsi22m4koia44kc5pcjr7nec2rlxyad.onion/tpo/core/torspec/-/blob/main/proposals/254-padding-negotiation.txt#L60-69

http://eweiibe6tdjsdprb4px6rqrzzcsi22m4koia44kc5pcjr7nec2rlxyad.onion/tpo/core/torspec/-/blob/main/tor-spec.txt#L2041

but the current behaviour is that the client negotiated max value is overridden to be >= consensus_nf_ito_high

http://eweiibe6tdjsdprb4px6rqrzzcsi22m4koia44kc5pcjr7nec2rlxyad.onion/tpo/core/tor/-/blob/main/src/core/or/channelpadding.c#L176-186