Bump PolyKit.Embedded from 2.0.30 to 3.0.4 (#253)

Author: dependabot[bot]

src/TestableHttpClient/TestableHttpClient.csproj

@@ -35,7 +35,7 @@
     <PackageReference Include="System.Net.Http" Version="4.3.4" />
     <PackageReference Include="System.Text.Json" Version="4.6.0" />
     <PackageReference Include="Perfors.UnreachableException" Version="1.0.0" />
-    <PackageReference Include="PolyKit.Embedded" Version="2.0.30" />
+    <PackageReference Include="PolyKit.Embedded" Version="3.0.4" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'net6.0'">