Update SectionUpdates.cs

[wstaelens]

performance: removes arraylist

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[huoyaoyuan]

Same as #120661 (comment), there's no boxing here. The usage of collections can be optimized much further here, for example sorting on List<T> directly.

[wstaelens]

Same as #120661 (comment), there's no boxing here. The usage of collections can be optimized much further here, for example sorting on List<T> directly.

feel free to further improve yourself, or accept this approvement.
regarding (un)boxing: true.

anyway: any gain is a gain.