fix: requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-FONTTOOLS-6133203
- https://snyk.io/vuln/SNYK-PYTHON-NUMPY-2321964
- https://snyk.io/vuln/SNYK-PYTHON-NUMPY-2321966
- https://snyk.io/vuln/SNYK-PYTHON-NUMPY-2321970

requirements.txt

@@ -26,3 +26,4 @@ requests>=2.31.0 # not directly required, pinned by Snyk to avoid a vulnerabilit
 pillow>=10.0.1 # not directly required, pinned by Snyk to avoid a vulnerability
 setuptools>=65.5.1 # not directly required, pinned by Snyk to avoid a vulnerability
 tornado>=6.3.3 # not directly required, pinned by Snyk to avoid a vulnerability
+fonttools>=4.43.0 # not directly required, pinned by Snyk to avoid a vulnerability