Revert "Update external editor page to explain presets (#4261)"

The PR in question hasn't been merged yet.

This reverts commit 3a78fd216ba246a6d81f6af07bad718dd043385d.

getting_started/editor/external_editor.rst

@@ -13,16 +13,10 @@ To enable an external text editor, browse to the relevant editor settings via:
 
 .. image:: img/editor_settings.png
 
-You can choose your editor from a list of presets, which will cause Godot to
-use appropriate values for the executable path and command line flags settings.
-
-If your editor is at an unusual path, you can override the preset default by
-changing the Exec Path setting to point at your editor.
-
-Alternatively, you can use the "Custom" option and fill out both settings by
-hand. The flags allow you to integrate the editor with Godot, passing it the
-file path to open and other relevant arguments. Godot will replace the
-following placeholders in the flags string:
+There are two fields: the executable path and command line flags. The flags
+allow you to integrate the editor with Godot, passing it the file path to open
+and other relevant arguments. Godot will replace the following placeholders in
+the flags string:
 
 +---------------------+-----------------------------------------------------+
 | Field in Exec Flags | Is replaced with                                    |