fix workflox

.github/workflows/rssguard.yml

@@ -12,19 +12,19 @@ jobs:
     runs-on: "${{ matrix.os }}"
     strategy:
       matrix:
-        os: [windows-2019, ubuntu-20.04, macos-10.15]
+        os: [windows-2019, ubuntu-18.04, macos-10.15]
         use_webengine: ["ON", "OFF"]
         use_qt5: ["ON", "OFF"]
         include:
           - os: windows-2019
             script_name: .\resources\scripts\github-actions\build-windows.ps1
-          - os: ubuntu-20.04
+          - os: ubuntu-18.04
             script_name: ./resources/scripts/github-actions/build-linux-mac.sh
           - os: macos-10.15
             script_name: ./resources/scripts/github-actions/build-linux-mac.sh
         exclude:
-          - os: ubuntu-20.04
-            use_qt5: "ON"
+          - os: ubuntu-18.04
+            use_qt5: "OFF"
           - os: macos-10.15
             use_qt5: "ON"
     steps: