Disable a failing test. (#50160)

Author: Sergey Andreenko

src/tests/JIT/opt/Structs/structcopies.csproj

@@ -5,6 +5,8 @@
   <PropertyGroup>
     <DebugType>None</DebugType>
     <Optimize>True</Optimize>
+    <!-- https://github.com/dotnet/runtime/issues/49954 -->
+    <JitOptimizationSensitive>True</JitOptimizationSensitive>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="$(MSBuildProjectName).cs" />