edit predictions: Do not require modifier if in leading space but just accepted a prediction (#24733)

This makes the tab tab tab experience smoother

Release Notes:

- N/A

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Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: as-cii <as-cii@zed.dev>
Co-authored-by: Danilo Leal <daniloleal09@gmail.com>
Co-authored-by: Antonio <antonio@zed.dev>
Co-authored-by: Ben <ben@zed.dev>