Remove Shade.nvim.

Causes too many problems (like `Mason` window being invisible).

lua/custom/plugins/shade.lua

@@ -1,14 +0,0 @@
-return {
-  "sunjon/Shade.nvim",
-  config = function()
-    require('shade').setup({
-      overlay_opacity = 50,
-      opacity_step = 1,
-      keys = {
-        -- brightness_up   = '<C-Up>',
-        -- brightness_down = '<C-Down>',
-        -- toggle          = '<Leader>s',
-      }
-    })
-  end
-}