Pin-point pyinstaller to 4.1 (4.2 probably recognize as false positive by antivirus)

.gitlab-ci.yml

@@ -287,7 +287,7 @@ windows_exe:
     # Install pyinstaller hooks from the master (Fix issue with v2020.7 concerning pyopengl support)
     - pip install git+https://github.com/pyinstaller/pyinstaller-hooks-contrib.git
     # Install pyinstaller
-    - pip install pyinstaller
+    - pip install pyinstaller==4.1
     # Generate fat binary
     - cd package
     - cd windows