Fix a bug in update_state

In OpenGLContext.h, the `bindTexture` method attempts to unbind the
previous texture target when the target changes for a specific unit.
However, due to the behavior of update_state, it ends up unbinding the
new target instead.

Fix this by storing the state after functor execution, which is a more
natural logical flow.

filament/backend/src/opengl/OpenGLContext.h

@@ -639,8 +639,8 @@ private:
     template <typename T, typename F>
     static inline void update_state(T& state, T const& expected, F functor, bool force = false) noexcept {
         if (UTILS_UNLIKELY(force || state != expected)) {
-            state = expected;
             functor();
+            state = expected;
         }
     }