[TF2] Revert rate limit for the command tf_max_voice_speak_delay

[FangMeLater]

The bots used to be able to intentionally spamming "voicemenu" command to crash servers, but now that the "net_chan_limit_msec" command is in place, they would get kicked immediately for trying. I suggest to revert the hardcoded rate limit of 0.3 from the "voicemenu" command since it is no longer an exploitable issue anymore, also uncap tf_max_voice_speak_delay to allow the value to go below 0.