Fix deprecated errors + get multiple completions in one time

[HendrikPetertje]

This branch gets rid of deprecation errors and allows copilot-cmp to receive multiple suggestions.

Can't wait for the merge (source repo is pretty dead)? require this auto completion source instead:

{
 ...
 {
    'hendrikpetertje/copilot-cmp',
    branch = 'fix-deprecated-errors'
  }
}