Update s2n revision for docker s2n tests.
Update s2n revision for docker s2n tests.

This updates the HMAC proof to fix a bug that was revealed by the
more strict checking of pointer freshness.

GaloisInc/saw-script,GaloisInc/saw-script,GaloisInc/saw-script,GaloisInc/saw-script,GaloisInc/saw-script