Ignore safety vulnerabeility 72715 (#251)

# Description
See https://data.safetycli.com/v/72715/97c/

Seems not to work to update to mkdocs-material>=9.5.32. Just ignoring
the issue instead...

## Type of change
- [x] Bug fix and code cleanup
- [ ] New feature
- [ ] Documentation update
- [ ] Testing


## Checklist for the reviewer
This checklist should be used as a help for the reviewer.

- [ ] Is the change limited to one issue?
- [ ] Does this PR close the issue?
- [ ] Is the code easy to read and understand?
- [ ] Do all new feature have an accompanying new test?
- [ ] Has the documentation been updated as necessary?
- [ ] Is the code properly tested?

.github/workflows/ci_tests.yml

@@ -36,12 +36,14 @@ jobs:
       #  https://pyup.io/vulnerabilities/CVE-2021-34141/44717/
       # 70612: Jinja2 vulnerability. Only used as subdependency for mkdocs++ in tripper.
       #  https://data.safetycli.com/v/70612/97c/
+      #  https://data.safetycli.com/v/72715/97c/   # update to mkdocs>=9.5.32
       safety_options: |
         --ignore=48547
         --ignore=44715
         --ignore=44716
         --ignore=44717
         --ignore=70612
+        --ignore=72715
 
       ## Build package
       run_build_package: true