doc: Update the document of `getroute`about excluding nodes

doc/lightning-getroute.7

@@ -45,8 +45,10 @@ default is 5\.0, or up to 5% fee distortion\.
 
 
 \fIexclude\fR is a JSON array of short-channel-id/direction (e\.g\. [
-"564334x877x1/0", "564195x1292x0/1" ]) which should be excluded from
-consideration for routing\. The default is not to exclude any channels\.
+"564334x877x1/0", "564195x1292x0/1" ]) or node-id which should be excluded
+from consideration for routing\. The default is not to exclude any channels
+or nodes\. Note if the source or destination is excluded, the command result
+is undefined\.
 
 
 \fImaxhops\fR is the maximum number of channels to return; default is 20\.

doc/lightning-getroute.7.md

@@ -40,8 +40,10 @@ route generated. 0.0 means the exact fee of that channel is used, while
 default is 5.0, or up to 5% fee distortion.
 
 *exclude* is a JSON array of short-channel-id/direction (e.g. \[
-"564334x877x1/0", "564195x1292x0/1" \]) which should be excluded from
-consideration for routing. The default is not to exclude any channels.
+"564334x877x1/0", "564195x1292x0/1" \]) or node-id which should be excluded
+from consideration for routing. The default is not to exclude any channels
+or nodes. Note if the source or destination is excluded, the command result
+is undefined.
 
 *maxhops* is the maximum number of channels to return; default is 20.