Remove unused SNOW field which triggers legacy mode

[JLyne]

Description

There is a SNOW field in BlockEventListener which seems to be a remnant of handling the introduction of powdered snow in 1.17. I can find no uses of this field, and snow-related code in this file uses Tag.SNOW directly.

The material iteration for setting this field is also unnecessarily triggering the legacy material system, so it is best removed.

Submitter Checklist

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1. Make sure you are opening from a topic branch (/feature/fix/docs/ branch (right side)) and not your main branch.
2. Ensure that the pull request title represents the desired changelog entry.
3. New public fields and methods are annotated with @since TODO.
4. I read and followed the contribution guidelines.

[PierreSchwang]

LGTM