Eliminate use-after-move (flutter#34197)

pipeline_desc is a std::optional<PipelineDescriptor>. It's used in test
expectations after (lines 320-321) the move. This passes by value like
in other tests.

Author: cbracken

impeller/renderer/renderer_unittests.cc

@@ -285,9 +285,8 @@ TEST_P(RendererTest, CanRenderToTexture) {
   auto pipeline_desc =
       BoxPipelineBuilder::MakeDefaultPipelineDescriptor(*context);
   ASSERT_TRUE(pipeline_desc.has_value());
-  auto box_pipeline = context->GetPipelineLibrary()
-                          ->GetRenderPipeline(std::move(pipeline_desc))
-                          .get();
+  auto box_pipeline =
+      context->GetPipelineLibrary()->GetRenderPipeline(pipeline_desc).get();
   ASSERT_TRUE(box_pipeline);
 
   VertexBufferBuilder<VS::PerVertexData> vertex_builder;