fix: skip useless redraws when not running in Neovide

[dmitmel]

This is a follow-up to #1582. As far as I understand correctly, nvim__redraw is necessary to flush the changes to the neovim UI grid, which does not result in an immediate update if rendering is temporarily suspended by Neovide, but in all other types of UI this does result in an immediate redraw, such as when selecting different completion items with CTRL-N/CTRL-P. Compare:

without my PR:

before.mp4

with this PR:

after.mp4

I was able to notice this because my statusline shows when I am in the popup completion mode (i.e. when mode(1) returns ic, ix or similar), but also, notice that the cursor quickly jumps around in the inserted line. Also, I am pretty sure that the function utils.defer_neovide_redraw is supposed to go in utils.lua, not text_edits.lua.

[Saghen]

Thank you!