fix: Update deprecated health checks for vim.health

[bkp5190]

Description

Update deprecated vim.health references so :checkhealth jupytext works properly.

Using the following configuration through nixvim:

    jupytext = {
      enable = true;
      package = pkgs.vimUtils.buildVimPlugin {
        pname = "jupytext.nvim";
        src = pkgs.fetchgit {
          url = "https://github.com/bkp5190/jupytext.nvim";
          branchName = "deprecated-healthcheck";
          rev = "695295069a3aac0cf9a1b768589216c5b837b6f1";
          sha256 = "sha256-W6fkL1w2dYSjpAYOtBTlYjd2CMYPB596NQzBylIVHrE=";
        };
      };
    };

[vandalt]

I think this is a duplicate of #33, #25, #29 and #35