Bump pygments from 2.6.1 to 2.7.4

Bumps [pygments](https://github.com/pygments/pygments) from 2.6.1 to 2.7.4.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](pygments/pygments@2.6.1...2.7.4)

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

Author: dependabot[bot]

requirements.txt

@@ -52,7 +52,7 @@ pickleshare==0.7.5
 prometheus-client==0.8.0
 prompt-toolkit==3.0.5
 ptyprocess==0.6.0
-Pygments==2.6.1
+Pygments==2.7.4
 pyparsing==2.4.7
 pyrsistent==0.16.0
 PySocks==1.7.1