stb-tester-0.19-1.fc20.src.rpm: Corrected specfile

The specfile was missing the "moreutils" dependency added in
https://github.com/drothlis/stb-tester/commit/834b7953

I had missed the change because "make all" didn't regenerate
stb-tester.spec from stb-tester.spec.in. That's fixed
(https://github.com/drothlis/stb-tester/commit/8434d30b)
and in future I'm going to automate the release process further.