Deprecate the endpoint_uris field, as it is unused.

PiperOrigin-RevId: 296357191

google/spanner/admin/instance/v1/spanner_instance_admin.proto

@@ -398,14 +398,7 @@ message Instance {
   // allow "_" in a future release.
   map<string, string> labels = 7;
 
-  // Output only. The endpoint URIs based on the instance config.
-  // For example, instances located in a specific cloud region (or multi region)
-  // such as nam3, would have a nam3 specific endpoint URI.
-  // This URI is to be used implictly by SDK clients, with fallback to default
-  // URI. These endpoints are intended to optimize the network routing between
-  // the client and the instance's serving resources.
-  // If multiple endpoints are present, client may establish connections using
-  // any of the given URIs.
+  // Deprecated. This field is not populated.
   repeated string endpoint_uris = 8;
 }