MyMonitor: doesn't support showing NT/U21 last/next match

[dominiquelee]

MyMonitor cannot display matches for NT and U21 teams:

See https://github.com/minj/foxtrick/blob/c134de0234124520370c4eb16032f798ee92dc64/content/information-aggregation/my-monitor.js#L535-L540

NT matches should most likely be retrieved from nationalteammatches (which does not take a teamId parameter, only whether we want NT or U21 matches) and filtered from there. Ideally, only one call is made even if multiple NT teams are tracked in MyMonitor (and no call at all if there is none). Please note that team.type in this function is currently equal to nt for both NT and U21 teams, so extra parsing is needed.