core: remove Surface.shouldClose

This was a noop in all of our apprts and I think is a holdover from the
glfw days.

src/App.zig

@@ -132,18 +132,6 @@ pub fn destroy(self: *App) void {
 /// events. This should be called by the application runtime on every loop
 /// tick.
 pub fn tick(self: *App, rt_app: *apprt.App) !void {
-    // If any surfaces are closing, destroy them
-    var i: usize = 0;
-    while (i < self.surfaces.items.len) {
-        const surface = self.surfaces.items[i];
-        if (surface.shouldClose()) {
-            surface.close(false);
-            continue;
-        }
-
-        i += 1;
-    }
-
     // Drain our mailbox
     try self.drainMailbox(rt_app);
 }

src/apprt/embedded.zig

@@ -705,15 +705,6 @@ pub const Surface = struct {
         );
     }
 
-    pub fn setShouldClose(self: *Surface) void {
-        _ = self;
-    }
-
-    pub fn shouldClose(self: *const Surface) bool {
-        _ = self;
-        return false;
-    }
-
     pub fn getCursorPos(self: *const Surface) !apprt.CursorPos {
         return self.cursor_pos;
     }

src/apprt/gtk-ng/Surface.zig

@@ -30,11 +30,6 @@ pub fn close(self: *Self, process_active: bool) void {
     _ = process_active;
 }
 
-pub fn shouldClose(self: *Self) bool {
-    _ = self;
-    return false;
-}
-
 pub fn getTitle(self: *Self) ?[:0]const u8 {
     _ = self;
     return null;

src/apprt/gtk/Surface.zig

@@ -877,15 +877,6 @@ pub fn controlInspector(
     };
 }
 
-pub fn setShouldClose(self: *Surface) void {
-    _ = self;
-}
-
-pub fn shouldClose(self: *const Surface) bool {
-    _ = self;
-    return false;
-}
-
 pub fn getContentScale(self: *const Surface) !apprt.ContentScale {
     const gtk_scale: f32 = scale: {
         const widget = self.gl_area.as(gtk.Widget);