remove rarely used AI plugin

lua/custom/plugins/codeium.lua

@@ -1,9 +0,0 @@
-return {
-  -- Free Github Copilot alternative
-  'Exafunction/codeium.vim',
-  event = 'BufEnter',
-  config = function()
-    -- Set keymap to open chat in browser
-    vim.keymap.set('n', '<leader>cc', ':execute codeium#Chat()<Enter>', { desc = '[C]odeium [C]hat' })
-  end,
-}