Per some feedback in PHPLIB-1055, it would be more helpful for users to include type unions in doc method signatures (e.g. MongoDB\Database::command() instead of just the parameter table that follows.

This was likely never considered for PHPLIB-599 since we could not utilize PHP 8.0's type unions when implementing other typing improvements in PHPLIB-600; however, there's no technical reason we can't start documenting this, especially since those type requires are already enforced in various places (e.g. operation constructors).