fix: requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-PYINSTALLER-12579198

Author: snyk-bot

requirements.txt

@@ -2,5 +2,5 @@ fpdf2==2.7.6
 pathspec==0.11.2
 pypdf==3.17.0
 Pygments==2.15.1
-pyinstaller==5.13.1
+pyinstaller==6.0.0
 pytest==7.3.1