Fix info text

Removed ale_virualtext_prefix from debugging since it's not requried for
the functionality to work.
Sorted debugging info to make the list easier to navigate/diff.

autoload/ale/debugging.vim

@@ -53,7 +53,6 @@ let s:global_variable_list = [
 \    'ale_type_map',
 \    'ale_use_global_executables',
 \    'ale_virtualtext_cursor',
-\    'ale_virtualtext_prefix',
 \    'ale_warn_about_trailing_blank_lines',
 \    'ale_warn_about_trailing_whitespace',
 \]