Fix colors not being reset on (partial) accept w/ recent ZSH (fixes #789)

[ElementW]

The ZSH manual describes region_highlight as being an array in https://zsh.sourceforge.io/Doc/Release/Zsh-Line-Editor.html#Character-Highlighting, therefore the previous strategy of removing as many characters as the last suggestion is not the way to do it, explaining why it broke on recent ZSH versions.

Replace this logic with a simple last-element delete. Keeps the _ZSH_AUTOSUGGEST_LAST_HIGHLIGHT variable intact since there's no downside in tracking its content, as it still used as a marker for whether a suggestion highlight was applied.

Fixes #789.

[tomasnorre]

I can confirm that this fix solves the problem I have in #789

[ErwanGarreau]

I had the exact same problem (the zsh-autosuggestions proposed color was not changing back although it was accepted). This commit also fixed it for me. Thank you !

[rylwin]

This commit also fixes it for me, too. I started experiencing this issue after upgrading to Ubuntu 24.04 (from 22.04)

$  zsh --version
zsh 5.9 (x86_64-ubuntu-linux-gnu)

[dolphin-cat]

also fixes it for me, #820

[enoryw]

What's preventing this from getting merged?

[rieje]

Fixed for me too. Can this be merged? It's nearly a year and colors being broken for an autosuggestion plugin that relies on colors is kind of essential...

[rbjorklin]

I was having the same problem until I started using the code from this PR.

@ericfreese any chance you have a moment to review and merge?