Replace DISALLOW_COPY_AND_ASSIGN with deleted constructor. BUG=b:190446478 TEST=CQ Change-Id: I89ffcaa8443f761f32380504de1ac6ae5b200510 Reviewed-on: https://chromium-review.googlesource.com/c/weave/libweave/+/3017632 Reviewed-by: Grace Cham <hscham@chromium.org> Commit-Queue: Qijiang Fan <fqj@google.com> Tested-by: Qijiang Fan <fqj@google.com>