fix: Assume recurser ID is an int and document ID is a string

[jdkaplan]

The cron jobs failed to run today because PB panicked while trying to un-skip someone for tomorrow.

Zulip report

2024/08/14 04:00:01 server.go:3418: http: panic serving 127.0.0.1:38996: interface conversion: interface {} is int64, not string
...
main.(*FirestoreRecurserDB).UnsetSkippingTomorrow(0xc000062440, {0xcf20f8, 0xc00042c0a0}, {0xb2144, {0xc0004f62e0, 0x1b}, {0xc0001408b8, 0x17}, 0x1, 0xc0001e7080, ...})
    /layers/google.go.appengine-gomod/srv/database.go:254 +0x4a5
main.(*PairingLogic).match(0xc0000a6980, {0xcf0d70, 0xc00009e000}, 0xc000496000)
    /layers/google.go.appengine-gomod/srv/pairing_bot.go:136 +0x425
...

It looks like the issue is the assumption that the document ID == the recurser ID, but one is a string and the other is an int.

If this works (I don't have time to test it because I'm about to be traveling!), then it should be enough to manually run the pairing cron job again to make today's pairings.