SHA-256 not supported for RSA encryption

I'm trying to verify the [Azure attestation signature](https://learn.microsoft.com/en-us/azure/virtual-machines/instance-metadata-service?tabs=linux#response-2) using this library and am able to successfully parse the signature, but validation fails with the following error.
```
pkcs7: unsupported digest "1.2.840.113549.1.1.11" for encryption algorithm "1.2.840.113549.1.1.1"
```