highlighters: Rename entry points.

This tracks the API change made in the previous commit, as suggested in the
(#if 0'd) deprecation warning.

highlighters/line/line-highlighter.zsh

@@ -32,13 +32,13 @@
 : ${ZSH_HIGHLIGHT_STYLES[line]:=}
 
 # Whether the root highlighter should be called or not.
-_zsh_highlight_line_highlighter_predicate()
+_zsh_highlight_highlighter_line_predicate()
 {
   _zsh_highlight_buffer_modified
 }
 
 # root highlighting function.
-_zsh_highlight_line_highlighter()
+_zsh_highlight_highlighter_line_paint()
 {
   _zsh_highlight_add_highlight 0 $#BUFFER line
 }