ci: remove deprecated ubuntu 20.04, add new windows 2025 and macos 15

Author: Giuncan

.github/workflows/main.yml

@@ -25,10 +25,10 @@ jobs:
     strategy:
       matrix:
         os:
+          - windows-2025
           - windows-2022
           - ubuntu-24.04
           - ubuntu-22.04
-          - ubuntu-20.04
         turbovnc-version:
           - "3.1"
           # - "2.2.7"
@@ -37,6 +37,8 @@ jobs:
             turbovnc-version: "none"
           - os: macos-14
             turbovnc-version: "none"
+          - os: macos-15
+            turbovnc-version: "none"
 
     # The type of runner that the job will run on
     runs-on: ${{ matrix.os }}