update bookmaker build docs

Bookmaker can be run on one command line with:
./out/skia/bookmaker -E && ~/go/bin/fiddlecli --quiet && ./out/skia/bookmaker
Update the documentation to say so.

NOTRY=true
TBR=jcgregorio@google.com

Docs-Preview: https://skia.org/?cl=167385
Bug: skia:
Change-Id: I14bf660860c9a4451dce783b45b2b0ed02a59af9
Reviewed-on: https://skia-review.googlesource.com/c/167385
Commit-Queue: Cary Clark <caryclark@skia.org>
Commit-Queue: Joe Gregorio <jcgregorio@google.com>
Auto-Submit: Cary Clark <caryclark@skia.org>
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
Reviewed-by: Cary Clark <caryclark@skia.org>
2 files changed