Fix y clipping defaults

[leMaik]

We very frequently get questions about chunks seemingly not loading due to y clipping not being set correctly.

The problem could be the default values that are saved as a persistent setting – we should drop them imho. Instead, we should always use the values specified in the map view to avoid surprises.

Examples:

• https://old.reddit.com/r/chunky/comments/1dw3r8j/need_help_chunky_doesnt_load_chunks/
• https://old.reddit.com/r/chunky/comments/19c2pvb/do_you_know_guys_why_my_chunky_dont_render_above/
• https://old.reddit.com/r/chunky/comments/xmdwcv/any_idea_why_the_second_half_of_my_build_isnt/

[Peregrine05]

It seems to be the case that if the chunks are loaded before the Scene tab is opened, it uses [0, 256] as the Y range. But, if you first open the Scene tab, then the values are set properly.