fix(firebase_ui_auth): pass breakpoint from RegisterScreen to LoginScreen

[PKeviin]

Description

Pass the breakpoint from RegisterScreen to LoginScreen.
Changing the breakpoint had no effect on the RegisterScreen.

Checklist

• 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 (melos run analyze) does not report any problems on my PR.
• I read and followed the [Flutter Style Guide].
• I signed the [CLA].
• 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.
• No, this is not a breaking change.

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[lesnitsky]

@PKeviin could you please sign the CLA?

[PKeviin]

@lesnitsky It's ok

All contributors are covered under a CLA with Google