fix(android_alarm_manager_plus): Remove deprecated method registerWith

[nohli]

Description

The recently merged PR #495 didn't include the removal for this package, because the tests were failing (and to not have too much overhead, I reverted the changes).

This PR does the same as #495, but for android_alarm_manger_plus, and the checks are successful this time (couldn't check the reason locally because the tests use melos, maybe just had to add static in line 43/44).

Checklist

Before you create this PR confirm that it meets all requirements listed below by checking the relevant checkboxes ([x]).
This will ensure a smooth and quick review process. Updating the pubspec.yaml and changelogs is not required.

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See Contributor Guide).
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
• The analyzer (flutter analyze) does not report any problems on my PR.
• I read and followed the Flutter Style Guide.
• I am willing to follow-up on review comments in a timely manner.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change (please indicate a breaking change in CHANGELOG.md and increment major revision).
• No, this is not a breaking change.

[miquelbeltran]

LGTM!

[miquelbeltran]

merged and published