Bump flask from 0.12.3 to 1.0

Bumps [flask](https://github.com/pallets/flask) from 0.12.3 to 1.0.
- [Release notes](https://github.com/pallets/flask/releases)
- [Changelog](https://github.com/pallets/flask/blob/master/CHANGES.rst)
- [Commits](pallets/flask@0.12.3...1.0)

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

Author: dependabot[bot]

requirements.txt

@@ -1,4 +1,4 @@
-Flask==0.12.3
+Flask==1.0
 Flask-RESTful==0.2.12
 gensim==0.12.3