dev.boringcrypto: update BoringCrypto module to cert 3678

[FiloSottile]

There is a new certified version of BoringCrypto, so we should update the module for Go 1.16.

https://csrc.nist.gov/projects/cryptographic-module-validation-program/certificate/3678

[gopherbot]

Change https://golang.org/cl/263997 mentions this issue: [dev.boringcrypto] crypto/internal/boring: update BoringCrypto module to certificate 3678