Bump Microsoft.AspNetCore.TestHost from 8.0.19 to 8.0.20

---
updated-dependencies:
- dependency-name: Microsoft.AspNetCore.TestHost
  dependency-version: 8.0.20
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

test/OpenPolicyAgent.Opa.AspNetCore.Tests/OpenPolicyAgent.Opa.AspNetCore.Tests.csproj

@@ -11,7 +11,7 @@
 
   <!-- Normal Package Includes. -->
   <ItemGroup>
-    <PackageReference Include="Microsoft.AspNetCore.TestHost" Version="8.0.19" />
+    <PackageReference Include="Microsoft.AspNetCore.TestHost" Version="8.0.20" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
     <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
     <PackageReference Include="Testcontainers" Version="4.7.0" />