fix(firebase_ui_auth): Add padding between avatar and display name form

[EArminjon]

Description

There is no padding between avatar and display name form.

Related Issues

When user want to custom a bit the UI, it is difficult to proceed.

After :

Padding added is the same as the one used for non editing.

Checklist

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• 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.
• All unit tests pass (melos run test:unit:all doesn't fail).
• I read and followed the Flutter Style Guide.
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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.

[github-actions]

Hello 👋, this PR has been opened for more than 2 months with no activity on it.

If you think this is a mistake please comment and ping a maintainer to get this merged ASAP! Thanks for contributing!

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[EArminjon]

What is the value of this bot on PULL REQUEST

[EArminjon]

Hello @russellwheatley ,

Multiple PR are opens, can we have some review :) ?