Bump joblib from 0.12.5 to 1.2.0 in /requirements

Bumps [joblib](https://github.com/joblib/joblib) from 0.12.5 to 1.2.0.
- [Release notes](https://github.com/joblib/joblib/releases)
- [Changelog](https://github.com/joblib/joblib/blob/master/CHANGES.rst)
- [Commits](https://github.com/joblib/joblib/compare/0.12.5...1.2.0)

---
updated-dependencies:
- dependency-name: joblib
  dependency-type: direct:production
...

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

requirements/build.txt

@@ -15,7 +15,7 @@ greenlet==0.4.15
 gunicorn==19.9.0
 idna==2.7
 itsdangerous==1.1.0
-joblib==0.12.5
+joblib==1.2.0
 numpy==1.16.1
 pandas==0.23.4
 protobuf==3.13.0