lnrpc+routing: Only accept a single route for SendToRoute

lnrpc/rpc.proto

@@ -896,13 +896,7 @@ message SendToRouteRequest {
     /// An optional hex-encoded payment hash to be used for the HTLC.
     string payment_hash_string = 2;
 
-    /**
-    Deprecated. The set of routes that should be used to attempt to complete the
-    payment. The possibility to pass in multiple routes is deprecated and 
-    instead the single route field below should be used in combination with the 
-    streaming variant of SendToRoute.
-    */
-    repeated Route routes = 3 [deprecated = true];
+    reserved 3;
 
     /// Route that should be used to attempt to complete the payment.
     Route route = 4;

lnrpc/rpc.swagger.json

@@ -3216,13 +3216,6 @@
           "type": "string",
           "description": "/ An optional hex-encoded payment hash to be used for the HTLC."
         },
-        "routes": {
-          "type": "array",
-          "items": {
-            "$ref": "#/definitions/lnrpcRoute"
-          },
-          "description": "*\nDeprecated. The set of routes that should be used to attempt to complete the\npayment. The possibility to pass in multiple routes is deprecated and \ninstead the single route field below should be used in combination with the \nstreaming variant of SendToRoute."
-        },
         "route": {
           "$ref": "#/definitions/lnrpcRoute",
           "description": "/ Route that should be used to attempt to complete the payment."