While looking into CDRIVER-3227 I realized that the PCCERT_CONTEXT pointer, which is initialized by CertSetCertificateContextProperty in mongoc_secure_channel_setup_certificate_from_file, is never freed.

Based on this program example in Microsoft's documentation, it looks like we should free the pointer with CertFreeCertificateContext.

I do see that the allocated PCCERT_CONTEXT is later passed to AcquireCredentialsHandle via the SCHANNEL_CRED struct, so perhaps it is ultimately freed later on. If so, there may be nothing to fix here.