Bump mistune from 0.8.4 to 2.0.3

Bumps [mistune](https://github.com/lepture/mistune) from 0.8.4 to 2.0.3.
- [Release notes](https://github.com/lepture/mistune/releases)
- [Changelog](https://github.com/lepture/mistune/blob/master/docs/changes.rst)
- [Commits](https://github.com/lepture/mistune/compare/v0.8.4...v2.0.3)

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

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

requirements.txt

@@ -34,7 +34,7 @@ lazy-object-proxy==1.4.3
 MarkupSafe==1.1.1
 matplotlib==3.2.1
 mccabe==0.6.1
-mistune==0.8.4
+mistune==2.0.3
 mkl-fft==1.0.15
 mkl-random==1.1.0
 mkl-service==2.3.0