Update CI for Qt 6.9.0

Author: pifopi

.github/workflows/cpp-ci-serial-programs.yml

@@ -10,13 +10,13 @@ jobs:
       fail-fast: false
       matrix:
         os: [windows-2022, macos-13, ubuntu-24.04]
-        qt_version: ['5.12.12', '6.8.2']
+        qt_version: ['5.12.12', '6.9.0']
         include:
         - qt_version: '5.12.12'
           qt_version_major: '5'
           qt_modules: ''
 
-        - qt_version: '6.8.2'
+        - qt_version: '6.9.0'
           qt_version_major: '6'
           qt_modules: 'qtmultimedia qtserialport'