fix(history): address PR #116 review feedback

- console: drop orphaned `/logging chat` reference from
  cons_privacy_setting() — the subcommand was removed, PREF_CHLOG now
  tracks PREF_HISTORY implicitly
- console: delete cons_logging_setting() and remove its call from
  cons_show_log_prefs() — every line in it referenced /logging chat or
  /logging group, both now invalid after the deprecation below
- command: deprecate /logging command. It now prints a single notice
  pointing to /history; CMD_PREAMBLE trimmed (min_args=0, no
  setting_func, syntax/args/examples dropped); subcommand 'group'
  removed from autocomplete

The SQLite history-load gap for /correction off is split out into a
follow-up — out of scope for this PR.

src/command/cmd_defs.c

@@ -1660,19 +1660,14 @@ static const struct cmd_t command_defs[] = {
     },
 
     { CMD_PREAMBLE("/logging",
-                   parse_args, 2, 3, &cons_logging_setting)
+                   parse_args, 0, 3, NULL)
       CMD_MAINFUNC(cmd_logging)
       CMD_TAGS(
               CMD_TAG_CHAT)
       CMD_SYN(
-              "/logging group on|off")
+              "/logging")
       CMD_DESC(
-              "Configure groupchat (MUC) logging. "
-              "Regular chat logging is controlled by /history.")
-      CMD_ARGS(
-              { "group on|off", "Enable/Disable groupchat (room) logging." })
-      CMD_EXAMPLES(
-              "/logging group off")
+              "Deprecated. Use '/history' instead.")
     },
 
     { CMD_PREAMBLE("/states",