[9.x] fix: bring back old behaviour

[ankurk91]

Hi,

This PR bring back old behavior, since this can be a breaking change for many.

$notifiable->routeNotificationFor('MethodWhichIsNotImplemented', $notification);

// Larval 8.x and before => null
// Larval v9.x => throws UnhandledMatchError

The routeNotificationFor() method should return null if the method is not implemented on Notifiable.

Tip: the match expression does not return null when there is no match.

PS - This PR adds default case to some more match expressions.

[driesvints]

@ankurk91 would it be possible to go over #39583 and add the other places where this is needed to this PR as well? Seems like there's more of them.

[ankurk91]

@driesvints

I can do that, but looks like all of other match expression has a default case in the mentioned PR.
Only src/Illuminate/Notifications/RoutesNotifications.php was missed.

PS. - Added default case to missing places

[crynobone]

src/Illuminate/Database/Connection.php
src/Illuminate/Redis/RedisManager.php

[ankurk91]

@crynobone

Done!