Unbind the framebuffer when updating meshes.

While the vertex shaders used to update the meshes aren't actually rendering to the framebuffer, they may still refuse to run with some framebuffers bound - such as XR with multiple views.

drivers/gles3/storage/mesh_storage.cpp

@@ -1075,6 +1075,7 @@ void MeshStorage::update_mesh_instances() {
 	}
 
 	glEnable(GL_RASTERIZER_DISCARD);
+	glBindFramebuffer(GL_FRAMEBUFFER, 0);
 	// Process skeletons and blend shapes using transform feedback
 	while (dirty_mesh_instance_arrays.first()) {
 		MeshInstance *mi = dirty_mesh_instance_arrays.first()->self();