[Alipay] 直接引用 Portable.BouncyCastle，维持证书链验证工作

src/Essensoft.AspNetCore.Payment.Alipay/Essensoft.AspNetCore.Payment.Alipay.csproj

@@ -9,10 +9,12 @@
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.1'">
     <PackageReference Include="System.Text.Json" Version="4.7.0" />
     <PackageReference Include="Microsoft.Extensions.Http" Version="3.1.0" />
+    <PackageReference Include="Portable.BouncyCastle" Version="1.8.5.2" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'netcoreapp3.1'">
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
+    <PackageReference Include="Portable.BouncyCastle" Version="1.8.5.2" />
   </ItemGroup>
 
   <ItemGroup>