Remove stack driver image from gcp access validation (#1851)

Author: vishalbollu

pkg/types/clusterconfig/cluster_config_gcp.go

@@ -356,13 +356,6 @@ var GCPAccessValidation = &cr.StructValidation{
 				Validator: validateImageVersion,
 			},
 		},
-		{
-			StructField: "ImagePrometheusStackdriverSidecar",
-			StringValidation: &cr.StringValidation{
-				Default:   "quay.io/cortexlabs/prometheus-stackdriver-sidecar:" + consts.CortexVersion,
-				Validator: validateImageVersion,
-			},
-		},
 	},
 }