Fix test project

Author: andrewlock

tracer/test/Datadog.Trace.SourceGenerators.Tests/Datadog.Trace.SourceGenerators.Tests.csproj

@@ -6,7 +6,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.8.0" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="5.0.0" PrivateAssets="all" />
   </ItemGroup>
 
   <ItemGroup>