fix: requirements-test.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-FONTTOOLS-14151621

Author: snyk-bot

requirements-test.txt

@@ -13,3 +13,4 @@ xarray>=0.13
 wheel
 pyarrow
 zipp>=3.19.1 # not directly required, pinned by Snyk to avoid a vulnerability
+fonttools>=4.61.0 # not directly required, pinned by Snyk to avoid a vulnerability