The experiment which motivated CECPQ2b has concluded (although the
results haven't been published yet) and the SIKE code is causing some
issues for gRPC in gprc/grpc#20100. Also, this is code size that takes
up space in Android etc.

Change-Id: I43b0b8c420f236c0fe9b40bf2517d2fde98495d5
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/38384


Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>