Cocoa: Fix multiple methods warning

This fixes a warning due to us using bare ids and
NSCollectionLayoutAnchor having a message with the same name.

Original-Change: https://github.com/glfw/glfw/commit/bac15f94493938eded7161a7a0ab8827584e3db1
Change-Id: I5656acaf93ba93ed42e0f153bc7434623d3ff165
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/glfw/+/440919
Reviewed-by: John Rosasco <rosasco@google.com>
diff --git a/src/cocoa_window.m b/src/cocoa_window.m
index d648096..a7c7758 100644
--- a/src/cocoa_window.m
+++ b/src/cocoa_window.m
@@ -817,7 +817,7 @@
         [window->ns.object setLevel:NSMainMenuWindowLevel + 1];
     else
     {
-        [window->ns.object center];
+        [(NSWindow*) window->ns.object center];
         _glfw.ns.cascadePoint =
             NSPointToCGPoint([window->ns.object cascadeTopLeftFromPoint:
                               NSPointFromCGPoint(_glfw.ns.cascadePoint)]);