Bump flask from 0.12.2 to 1.0 in /bar-charts-bokeh-bottle-python-3

Bumps [flask](https://github.com/pallets/flask) from 0.12.2 to 1.0.
- [Release notes](https://github.com/pallets/flask/releases)
- [Changelog](https://github.com/pallets/flask/blob/master/CHANGES.rst)
- [Commits](pallets/flask@0.12.2...1.0)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Diff for: bar-charts-bokeh-bottle-python-3/requirements.txt

@@ -1,3 +1,3 @@
-flask==0.12.2
+flask==1.0
 bokeh==0.12.5
 pandas==0.20.1