Fix: stop using get_installed, use new treesitter api

[catgoose]

Fixes errors like:

E5108: Lua: vim/_core/editor.lua:0: nvim_exec2()[1]..BufReadPost Autocommands for "*": Vim(append):Lua callback: ...im/lazy/auto-fix-return.nvim/lua/auto-fix-return/lib.lua:35: attempt to call field 'get_installed' (a nil value)

I get these errors when I restart LSP or sometimes opening fff.nvim/telescope before LSP is initialized

[Jay-Madden]

Oh, interesting. did not realize nvim-treesitter.parsers could load before nvim-treesitter

thx for the fix