fix(texlab): remove deprecated texlab.auxDirectory

[Thibaulltt]

I noticed this while debugging some texlab problems.

The configuration key 'texlab.auxDirextory' has been deprecated, in favor of 'texlab.build.auxDir', mirroring the latexmkrc's auxDir variable.

see: https://github.com/latex-lsp/texlab/wiki/Configuration#deprecated-texlabauxdirectory

[justinmk]

needs a rebase, the server_configurations/ directory was renamed to configs/ #3330

[Thibaulltt]

Hi, forgot to push my commit a couple weeks ago and had to rebase again. Should be good to go now :)

[justinmk]

The configuration key 'texlab.auxDirextory' has been deprecated, in favor of 'texlab.build.auxDir', mirroring the latexmkrc's auxDir variable.

This PR didn't add 'texlab.build.auxDir' though. Is that intentional, not needed, or why? Always helpful to concisely mention that in a commit message / pr description.

[Thibaulltt]

Sorry for not mentionning it. It has a default value of . in texlab if not explicitly set, or if the user has no latexmkrc file. Since I use a latexmkrc file myself, this is auto-magically populated with the right value :)

Source: https://github.com/latex-lsp/texlab/wiki/Configuration#texlabbuildauxdirectory

[Thibaulltt]

Should I maybe include it anyway and let the user override it in their own setup({...}) call? Leaving it blank always ensures texlab is the one responsible for it, but I'd understand if you wanted a more complete config in this repo.

[justinmk]

It's good to delegate to defaults where possible, we just need to mention that for future reference, when we change things. I will add your note to the commit message.