talks: Fix misleading constant expression in taste.slide

The current text has "third=1/3", but 1/3 = 0. Make it 1.0/3 instead.

Change-Id: I19ea0e7ceb73b5526f53d62aa4308c8530d4eae6
Reviewed-on: https://go-review.googlesource.com/8162
Reviewed-by: Robert Griesemer <gri@golang.org>
1 file changed