Tests: Disable NavigationServer3D async bake test with race condition

tests/servers/test_navigation_server_3d.h

@@ -764,6 +764,8 @@ TEST_SUITE("[Navigation]") {
 		navigation_server->process(0.0); // Give server some cycles to commit.
 	}
 
+	// FIXME: The race condition mentioned below is actually a problem and fails on CI (GH-90613).
+	/*
 	TEST_CASE("[NavigationServer3D] Server should be able to bake asynchronously") {
 		NavigationServer3D *navigation_server = NavigationServer3D::get_singleton();
 		Ref<NavigationMesh> navigation_mesh = memnew(NavigationMesh);
@@ -781,6 +783,7 @@ TEST_SUITE("[Navigation]") {
 		CHECK_EQ(navigation_mesh->get_polygon_count(), 0);
 		CHECK_EQ(navigation_mesh->get_vertices().size(), 0);
 	}
+	*/
 }
 } //namespace TestNavigationServer3D