vi-mode: disable displayed mode on startup

This change had the unintended consequence of overriding the functions to ensure
that application mode was set to use $terminfo sequences, introduced in #6449.

Fixes #7137

plugins/vi-mode/vi-mode.plugin.zsh

@@ -4,11 +4,6 @@ function zle-keymap-select() {
   zle -R
 }
 
-# Ensures that MODE_INDITCATOR is displayed on terminal start up.
-function zle-line-init() {
-  zle reset-prompt
-}
-
 # Ensure that the prompt is redrawn when the terminal size changes.
 TRAPWINCH() {
   zle && { zle -R; zle reset-prompt }