gtk/atcontext: Cleanup a11y backends list

Declaring a separate entry for Wayland and X11 is not very useful when
both just end up calling the same constructor. Also, in theory, this
can cause the Wayland entry to be picked up on X11 if both backends
are enabled (which is the common case).

Not that it matters, since the 'name' field is unused.

Nonetheless, clean it up to be a single entry

gtk/gtkatcontext.c

@@ -604,11 +604,8 @@ static const struct {
                                      GtkAccessible    *accessible,
                                      GdkDisplay       *display);
 } a11y_backends[] = {
-#if defined(GDK_WINDOWING_WAYLAND)
-  { "AT-SPI (Wayland)", "atspi", gtk_at_spi_create_context },
-#endif
-#if defined(GDK_WINDOWING_X11)
-  { "AT-SPI (X11)", "atspi", gtk_at_spi_create_context },
+#if defined(GDK_WINDOWING_WAYLAND) || defined(GDK_WINDOWING_X11)
+  { "AT-SPI", "atspi", gtk_at_spi_create_context },
 #endif
   { "Test", "test", gtk_test_at_context_new },
 };