print one fewer digit than ideal

Implementation-specific rounding means that even if we've got the
shortest string that round trips, we might not have the same string.

I _think_ truncating the final digit will make everyone agree.
If not, I think we'll have to printf() ourselves.

Change-Id: I3a4daea7ac6c51015ce33fac3af75d5b4f057333
Reviewed-on: https://skia-review.googlesource.com/c/skcms/+/259822
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
66 files changed