Bump pygments from 2.9.0 to 2.15.0 (#396)

Bumps [pygments](https://github.com/pygments/pygments) from 2.9.0 to 2.15.0.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](pygments/pygments@2.9.0...2.15.0)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

dev-requirements.txt

@@ -24,7 +24,7 @@ markupsafe==2.0.1
     # via jinja2
 packaging==20.9
     # via sphinx
-pygments==2.9.0
+pygments==2.15.0
     # via sphinx
 pyparsing==2.4.7
     # via packaging

sourcedocs/requirements.txt

@@ -35,7 +35,7 @@ requests==2.31.0
 snowballstemmer==2.1.0
     # via sphinx
 sphinx==4.1.1
-    # via -r requirements.in
+    # via -r sourcedocs/requirements.in
 sphinxcontrib-applehelp==1.0.2
     # via sphinx
 sphinxcontrib-devhelp==1.0.2