Bump puremagic from 1.27 to 1.28

Bumps [puremagic](https://github.com/cdgriffith/puremagic) from 1.27 to 1.28.
- [Release notes](https://github.com/cdgriffith/puremagic/releases)
- [Changelog](https://github.com/cdgriffith/puremagic/blob/master/CHANGELOG.md)
- [Commits](cdgriffith/puremagic@1.27...1.28)

---
updated-dependencies:
- dependency-name: puremagic
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

requirements.txt

@@ -1,3 +1,3 @@
-puremagic==1.27
+puremagic==1.28
 pygraphviz==1.13
 svg.path==6.3