Use $CABAL_VERSION env var

Author: jneira

.azure/windows-stack.yml

@@ -104,7 +104,7 @@ jobs:
     displayName: "Install Runtime Test-Dependencies: hoogle database"
   - bash: |
       source .azure/windows-stack.bashrc
-      choco install -y cabal --version 3.0.0.0
+      choco install -y cabal --version $CABAL_VERSION
       /C/ProgramData/chocolatey/bin/RefreshEnv.cmd
     displayName: "Install Runtime Test-Dependencies: cabal"
   - bash: |