refactor: delete old firebase invites snippets

[thatfiredev]

Correct me if I'm wrong, but I think these snippets are no longer shown in the Docs.

[samtstern]

@rosariopfernandes I think you're right about the invites module but I think the dl-invites ones (or at least some of them) are still used on this page: https://firebase.google.com/docs/dynamic-links/use-cases/user-to-user

[thatfiredev]

@samtstern Oops, that's true. I'll update this PR to keep dl-invites

[samtstern]

@rosariopfernandes :

FAILURE: Build failed with an exception.
> Configure project :test-lab:app

* What went wrong:
Project 'invites' not found in root project 'snippets-android'. Some candidates are: 'dl-invites'.

[thatfiredev]

@samtstern Seems like we just spotted a flaw on our modular build 😆

The PR build is trying to build the invites module since it's the only one that contains changes and is not aware that it no longer exists 😅 :

Building Pull Request with
:invites:app:assembleDebug :invites:app:check

However, the build succeeds if we build the whole project.

[samtstern]

@rosariopfernandes ah that makes sense!