Temporarily disable super_editor tests

[loic-sharma]

We need to do a hard breaking change in Flutter that affects package:super_editor: flutter/flutter#180436

To workaround the hard breaking change, we will:

1. Temporarily remove super_editor from Flutter's customer tests (this PR)
2. Land the breaking change in Flutter.
3. Update super_editor's main branch to handle Flutter's breaking change.
4. Re-add super_editor to customer tests, using the latest commit from super_editor's main branch.

Why this is necessary...

To fix flutter/flutter#161592, we need to pass additional styling information to the web engine.

Historically, we plumb text styling information through TextInputConnection.setStyle(...). However, every time we add a parameter here, it creates a breaking change for super_editor's TextInputConnectionDecorator as it implements TextInputConnection.

To stop this cycle, we will do a one-time breaking change to move to a more extensible pattern:

1. Add new TextInputStyle class. This will wrap all text input styling properties.
2. Add new TextInputConnection.updateStyle(TextInputStyle style) method.
3. Deprecate TextInputConnection.setStyle(...).

This pattern lets us add more text input styling properties without breaking super_editor again.

To handle this breaking change, the following code will need to be added to super_editor's TextInputConnectionDecorator:

  @override
  void updateStyle(TextInputStyle style) => client?.updateStyle(style);

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read the Flutter Style Guide recently, and have followed its advice.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

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