Bump six from 1.11.0 to 1.12.0 (#65)

Bumps [six](https://github.com/benjaminp/six) from 1.11.0 to 1.12.0.
- [Release notes](https://github.com/benjaminp/six/releases)
- [Changelog](https://github.com/benjaminp/six/blob/master/CHANGES)
- [Commits](https://github.com/benjaminp/six/compare/1.11.0...1.12.0

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

requirements.txt

@@ -11,6 +11,6 @@ requests==2.21.0
 sciencebeam-alignment==0.0.2
 sciencebeam-utils==0.0.1
 sklearn-crfsuite==0.3.6
-six==1.11.0
+six==1.12.0
 tensorflow-transform==0.11.0
 tqdm==4.30.0