fix: requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-XMLTODICT-12427118

Author: snyk-bot

requirements.txt

@@ -8,7 +8,7 @@ pyquaternion==0.9.5
 pyvoro-mmalahe==1.3.4
 scipy>=1.10.1
 setuptools>=70.0.0 
-xmltodict==0.12.0
+xmltodict==0.15.0
 tox==3.14.0
 lsq-ellipse==2.0.1
 zipp>=3.19.1 # not directly required, pinned by Snyk to avoid a vulnerability