update flag to default to false

Author: jnlycklama

src/Microsoft.Health.Dicom.Web/appsettings.json

@@ -85,7 +85,7 @@
       "EnableOhifViewer": true,
       "EnableExternalStore": false,
       "DisableOperations": false,
-      "EnableExternalStoreHealthCheck": true
+      "EnableExternalStoreHealthCheck": false
     },
     "Services": {
       "DeletedInstanceCleanup": {