Back out "apprt/gtk: force X11 backend on GTK 4.14"

This backs out commit bb185cf.

This was breaking IME input for some users and overall I couldn't find
other users where this really fixed anything other than me so I'm going
to back this out and fix this using my own system.

src/apprt/gtk/App.zig

@@ -123,13 +123,6 @@ pub fn init(core_app: *CoreApp, opts: Options) !App {
         //     and initializing a Vulkan context was causing a longer delay
         //     on some systems.
         _ = internal_os.setenv("GDK_DEBUG", "opengl,gl-disable-gles,vulkan-disable");
-
-        // Wayland-EGL on GTK 4.14 causes "Failed to create EGL context" errors.
-        // This can be fixed by forcing the backend to prefer X11. This issue
-        // appears to be fixed in GTK 4.16 but I wasn't able to bisect why.
-        // The "*" at the end says that if X11 fails, try all remaining
-        // backends.
-        _ = internal_os.setenv("GDK_BACKEND", "x11,*");
     } else {
         // Versions prior to 4.14 are a bit of an unknown for Ghostty. It
         // is an environment that isn't tested well and we don't have a