Update backends.yml

Author: DarthAffe

.github/workflows/backends.yml

@@ -53,7 +53,7 @@ jobs:
           path: .\build\bin\Release\stable-diffusion.dll
 
   windows-cuda12:
-    runs-on: windows-latest
+    runs-on: windows-2019
 
     steps:
       - name: Checkout
@@ -111,7 +111,7 @@ jobs:
           path: .\build\bin\Release\stable-diffusion.dll
 
   windows-cuda11:
-    runs-on: windows-latest
+    runs-on: windows-2019
 
     steps:
       - name: Checkout