Fixed some logical and language typos:

• Toggling ping by alias no longer says you toggled sound (it did toggle alias pinging properly though)
• Tab autocomplete now works properly for /cping prefs toggle (off-by-1 error in code)

Adjusted some wording when toggling to neaten up the phrasing:

• Toggle sound: "Toggled sound to" -> "Toggled ping sound to"
• Toggle ping by alias: "Toggled aliases to" -> "Toggled ping by alias to"