Remove unused editor setting `editors/grid_map/editor_side`

This option is no longer used after the rework in GH-96922

doc/classes/EditorSettings.xml

@@ -519,9 +519,6 @@
 		</member>
 		<member name="editors/bone_mapper/handle_colors/unset" type="Color" setter="" getter="">
 		</member>
-		<member name="editors/grid_map/editor_side" type="int" setter="" getter="">
-			Specifies the side of 3D editor's viewport where GridMap's mesh palette will appear.
-		</member>
 		<member name="editors/grid_map/palette_min_width" type="int" setter="" getter="">
 			Minimum width of GridMap's mesh palette side panel.
 		</member>

editor/editor_settings.cpp

@@ -764,8 +764,6 @@ void EditorSettings::_load_defaults(Ref<ConfigFile> p_extra_config) {
 	_initial_set("editors/grid_map/palette_min_width", 230);
 	set_restart_if_changed("editors/grid_map/palette_min_width", true);
 	_initial_set("editors/grid_map/preview_size", 64);
-	// GridMapEditorPlugin
-	EDITOR_SETTING(Variant::INT, PROPERTY_HINT_ENUM, "editors/grid_map/editor_side", 1, "Left,Right");
 
 	// 3D
 	EDITOR_SETTING_BASIC(Variant::COLOR, PROPERTY_HINT_NONE, "editors/3d/primary_grid_color", Color(0.56, 0.56, 0.56, 0.5), "")