Bump pygments from 2.10.0 to 2.15.0

Bumps [pygments](https://github.com/pygments/pygments) from 2.10.0 to 2.15.0.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](pygments/pygments@2.10.0...2.15.0)

---
updated-dependencies:
- dependency-name: pygments
  dependency-type: indirect
...

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

requirements.txt

@@ -8,16 +8,12 @@ alabaster==0.7.12
     # via sphinx
 babel==2.9.1
     # via sphinx
-backports.entry-points-selectable==1.1.0
+backports-entry-points-selectable==1.1.0
     # via virtualenv
 certifi==2021.10.8
     # via requests
 charset-normalizer==2.0.7
     # via requests
-colorama==0.4.4
-    # via
-    #   sphinx
-    #   tox
 commonmark==0.9.1
     # via recommonmark
 distlib==0.3.3
@@ -49,7 +45,7 @@ pluggy==1.0.0
     # via tox
 py==1.10.0
     # via tox
-pygments==2.10.0
+pygments==2.15.0
     # via sphinx
 pyparsing==2.4.7
     # via packaging