docs(README): change forgotten breaking change in example (#2377)

README.md

@@ -76,7 +76,7 @@ lvim.keys.normal_mode["<C-s>"] = ":w<cr>"
 -- lvim.builtin.which_key.mappings["P"] = { "<cmd>Telescope projects<CR>", "Projects" }
 
 -- Configure builtin plugins
-lvim.builtin.dashboard.active = true
+lvim.builtin.alpha.active = true
 lvim.builtin.notify.active = true
 lvim.builtin.terminal.active = true