Remove redundant selection::Region type
Remove redundant selection::Region type

The type selection::Region was defined identially to std::ops::Range.
Using something other than range just served to confuse.

jwilm/alacritty,alacritty/alacritty,alacritty/alacritty,jwilm/alacritty,jwilm/alacritty,jwilm/alacritty