CAPZ: fix disabling Windows for ci-entrypoint

Author: nojnhuh

config/jobs/kubernetes-sigs/cluster-api-provider-azure/cluster-api-provider-azure-presubmits-main.yaml

@@ -692,7 +692,7 @@ presubmits:
           privileged: true
         env:
           - name: TEST_WINDOWS
-            value: "false"
+            value: "" # disabled
           - name: WINDOWS_SERVER_VERSION
             value: "windows-2022"
         resources:

config/jobs/kubernetes-sigs/cluster-api-provider-azure/cluster-api-provider-azure-presubmits-release-v1beta1.yaml

@@ -391,7 +391,7 @@ presubmits:
           privileged: true
         env:
           - name: TEST_WINDOWS
-            value: "false"
+            value: "" # disabled
           - name: WINDOWS_SERVER_VERSION
             value: "windows-2022"
         resources: