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

@@ -63,7 +63,7 @@ pyasn1==0.4.8
 pyasn1-modules==0.2.8
 pydicom @ file:///home/conda/feedstock_root/build_artifacts/pydicom_1590767348156/work
 pyface==6.1.2
-Pygments==2.6.1
+Pygments==2.7.4
 pyparsing==2.4.7
 pysurfer==0.11.0
 python-dateutil==2.8.1