Fix EC point-at-infinity key loading raising InternalError on AWS-LC

[DarkaMaul]

When updating #14598 to AWS-LC 1.72.0, an unrelated error appeared when running the test suite:

E           cryptography.exceptions.InternalError: Unknown OpenSSL error. This error is commonly encountered
E                               when another library is not cleaning up the OpenSSL error
E                               stack. If you are using cryptography with another library
E                               that uses OpenSSL try disabling it before reporting a bug.
E                               Otherwise please file an issue at
E                               https://github.com/pyca/cryptography/issues with
E                               information on how to reproduce this. (error:0F000077:elliptic curve routines:OPENSSL_internal:POINT_AT_INFINITY:/tmp/aws-lc/crypto/fipsmodule/ec/ec_key.c:210:)

I believe this was caused by the fix in aws/aws-lc#3101