In CL 122404, we change -replace syntax from => to =.
And we also need to change this and the tests.

Fixes golang/go#26373.

Change-Id: I2d4e85e10c1578540cc7673b93d849270940d776
Reviewed-on: https://go-review.googlesource.com/123778Reviewed-by: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>