home: vim: lualine: use built-in 'branch'

It now supports worktrees correctly (or at least I can't figure out
which issue I used to have with it...).

As a bonus, it also supports showing the correct branch for an `oil`
buffer.

This reverts commit 481d5f6f53.

modules/home/vim/plugin/settings/lualine.lua

@@ -30,7 +30,7 @@ lualine.setup({
             { "mode" },
         },
         lualine_b = {
-            { "FugitiveHead" },
+            { "branch" },
             { "filename", symbols = { readonly = "🔒" } },
         },
         lualine_c = {