Unable to disable key algo in ssh.minimum_key_sizes

[CirnoT]

As mentioned here #11417 (comment)

It is impossible to use -1 to disable algo for minimum key size check.

SSH.MinimumKeySizeCheck = sec.Key("MINIMUM_KEY_SIZE_CHECK").MustBool()
minimumKeySizes := Cfg.Section("ssh.minimum_key_sizes").Keys()
for _, key := range minimumKeySizes {
	if key.MustInt() != -1 {
		SSH.MinimumKeySizes[strings.ToLower(key.Name())] = key.MustInt()
	}
}