Mojom frontend: Update shortened url for latest version of graph-theory paper.

Both the goo.gl url shortener and pdf documents in Google docs are immutable
as far as I can tell. So the only way I can update a linked-to pdf is to upload
a new document and create a new shortened url. I considered using some url
shortener service besides goo.gl but I decided not to bother.

R=azani@chromium.org

Review URL: https://codereview.chromium.org/2028843002 .

mojom/mojom_tool/utils/wellfounded_graphs.go

diff --git a/mojom/mojom_tool/utils/wellfounded_graphs.go b/mojom/mojom_tool/utils/wellfounded_graphs.go
index 1266a96..6e2c32f 100644
--- a/mojom/mojom_tool/utils/wellfounded_graphs.go
+++ b/mojom/mojom_tool/utils/wellfounded_graphs.go
@@ -11,7 +11,7 @@
 
 // This file contains an implementation of an algorithm to check the well-foundedness
 // of two-sorted directed graphs. See the paper
-// "Well-Founded Two-Sorted Directed Graphs" (https://goo.gl/ipxFKu) for background
+// "Well-Founded Two-Sorted Directed Graphs" (https://goo.gl/YrLmfY) for background
 // and detailed definitions. Here we give only a high-level overview.
 //
 // A two-sorted graph is a directed graph that contains two sorts of nodes called circle nodes and