crypto/tls: remove unused hashForClientCertificate param

crypto/tls: remove unused hashForClientCertificate param

Change-Id: I86af2508a31ea1e79d362c22ff4fac8900536761
GitHub-Last-Rev: d2a1ddccbd32499d7c379941daff528e7f2017c3
GitHub-Pull-Request: golang/go#52328
Reviewed-on: https://go-review.googlesource.com/c/go/+/399829
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>