nvim: remove extension configuration from Telescope setup

This makes the Telescope plugin configuration more independent from
extensions. The next step would be to move the `fzf-native` extension to
its own file.

config/nvim/lua/fschauen/plugins/telescope-file-browser.lua

@@ -7,7 +7,7 @@ return {
   dependencies = "nvim-telescope/telescope.nvim",
 
   keys = {
-    { lhs("B"), "<cmd>Telescope file_browser<cr>", desc = desc("file [B]rowser") },
+    { lhs("B"), "<cmd>Telescope file_browser theme=ivy<cr>", desc = desc("file [B]rowser") },
   },
 
   config = function()

config/nvim/lua/fschauen/plugins/telescope.lua

@@ -177,9 +177,6 @@ return {
         colorscheme = { theme = "dropdown" },
         spell_suggest = { theme = "cursor" },
       },
-      extensions = {
-        file_browser = { theme = "ivy" },
-      },
     })
   end,