ci: use Windows 2019

Author: RobPasMue

.github/workflows/backwards_compatibility.yml

@@ -39,13 +39,13 @@ jobs:
         include:
           - image-tag: "windows-24.1"
             backend-version: "24.1"
-            windows-runner: "windows-2022"
+            windows-runner: "windows-2019"
           - image-tag: "windows-24.2"
             backend-version: "24.2"
-            windows-runner: "windows-2022"
+            windows-runner: "windows-2019"
           - image-tag: "windows-25.1"
             backend-version: "25.1"
-            windows-runner: "windows-2022"
+            windows-runner: "windows-2019"
           - image-tag: "core-windows-25.2"
             backend-version: "25.2"
             windows-runner: "windows-latest"