The CupertinoTextSelectionToolbar sets the maxWidth of the whole toolbar to the width of the first page. This ends up clipping other pages from the toolbar. This PR just removes this limitation.

It was easy enough that I thought there was a catch, but I ran the tests locally and they all passed.

|Before|After|
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|![Simulator Screenshot - iPhone Xʀ - 2023-11-09 at 19 45 29](https://github.com/flutter/flutter/assets/12024080/c84c40b9-3b02-48bf-9e87-17a9e4cfb461)|![Simulator Screenshot - iPhone Xʀ - 2023-11-09 at 19 44 30](https://github.com/flutter/flutter/assets/12024080/0c3d829b-952e-462b-9f02-8a2833c6f65d)|

https://github.com/flutter/flutter/issues/138177