Vulkan: legacy_dithering disallow reactivate when breaking RP

Hitting the assert in dEQP GLES2.functional.fragment_ops.random.0:
https://crsrc.org/c/third_party/angle/src/libANGLE/renderer/vulkan/ContextVk.cpp;drc=52fe3116ead9a5de51ddad17fcb14bf8ecb3a69d;l=2347

Bug: b/292259684
Change-Id: Ib40b90dde3b271c714b6181e4ba4d70f3e1b5e86
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4706174
Reviewed-by: Charlie Lao <cclao@google.com>
Auto-Submit: Roman Lavrov <romanl@google.com>
Commit-Queue: Roman Lavrov <romanl@google.com>

src/libANGLE/renderer/vulkan/ContextVk.cpp

@@ -5099,6 +5099,9 @@ void ContextVk::updateDither()
         FramebufferVk *framebufferVk = vk::GetImpl(mState.getDrawFramebuffer());
         if (framebufferVk->updateLegacyDither(this))
         {
+            // Can't reactivate: same framebuffer but the render pass desc has changed.
+            mAllowRenderPassToReactivate = false;
+
             onRenderPassFinished(RenderPassClosureReason::LegacyDithering);
         }
     }