Remove editor_double_embed

It's no longer needed after the `fix_local_coordinates()` change from a
fa12c64866a8b79e862bc5db4c4b092a4b762689.

src/common/configuration.cpp

@@ -101,12 +101,6 @@ Configuration::Configuration(const fs::path& config_path,
                 } else {
                     invalid_options.push_back(key);
                 }
-            } else if (key == "editor_double_embed") {
-                if (const auto parsed_value = value.as_boolean()) {
-                    editor_double_embed = parsed_value->get();
-                } else {
-                    invalid_options.push_back(key);
-                }
             } else if (key == "editor_force_dnd") {
                 if (const auto parsed_value = value.as_boolean()) {
                     editor_force_dnd = parsed_value->get();

src/common/configuration.h

@@ -94,20 +94,6 @@ class Configuration {
      */
     std::optional<boost::filesystem::path> disable_pipes;
 
-    /**
-     * If this is set to `true`, then the plugin editor should be embedded in
-     * yet another window. This would result in an embedding sequence of
-     * `<window_provided_by_host> <-> <wine_parent_window> <->
-     * <wine_child_window> <-> <window_created_by_plugin>`, where
-     * `<wine_child_window>` is the new addition. The only plugin I've
-     * encountered where this was necessary was PSPaudioware E27 (and it likely
-     * also applies to other PSPaudioware plugins with expandable GUIs). I also
-     * haven't noticed any issues caused from having this enabled, but having it
-     * behind a flag reduces the amount of moving parts so that's probably a
-     * better idea.
-     */
-    bool editor_double_embed = false;
-
     /**
      * If set to `true`, we'll remove the `XdndAware` property all ancestor
      * windows in `editor.cpp`. This is needed for REAPER as REAPER implements
@@ -202,7 +188,6 @@ class Configuration {
 
         s.ext(disable_pipes, bitsery::ext::InPlaceOptional(),
               [](S& s, auto& v) { s.ext(v, bitsery::ext::BoostPath{}); });
-        s.value1b(editor_double_embed);
         s.value1b(editor_force_dnd);
         s.value1b(editor_xembed);
         s.ext(frame_rate, bitsery::ext::InPlaceOptional(),