migrate nvim config to 0.12.0: vim.pack, ui2, snacks -> mini, just general spring cleaning

nvim/lua/diagnostics.lua

@@ -1,14 +1,6 @@
 local sev = vim.diagnostic.severity
 vim.diagnostic.config({
-    -- underline = true,
-    -- This enables the diagnostics at end of line
-    -- virtual_text = {
-    --     prefix = "●",
-    -- },
-    -- Disable this whilst using tiny inline diagnostics
     virtual_text = false,
-    -- This enables the separate buffer diagnostics
-    -- virtual_lines = true,
     update_in_insert = true,
     signs = {
         text = {