error-values.md: fix example output

Modify the example for detail-mode output to match the current implementation.

Change-Id: I0109fd6f51e787da06772b589d17dd7f73793629
Reviewed-on: https://go-review.googlesource.com/c/160977
Reviewed-by: Damien Neil <dneil@google.com>
diff --git a/design/29934-error-values.md b/design/29934-error-values.md
index f8d49d8..ec4387a 100644
--- a/design/29934-error-values.md
+++ b/design/29934-error-values.md
@@ -205,13 +205,17 @@
 ```
 write users database:
     more detail here
-    /path/to/database.go:111
+    mypkg/db.Open
+        /path/to/database.go:111
   - call myserver.Method:
-    /path/to/grpc.go:222
+    google.golang.org/grpc.Invoke
+        /path/to/grpc.go:222
   - dial myserver:3333:
-    /path/to/net/dial.go:333
+    net.Dial
+        /path/to/net/dial.go:333
   - open /etc/resolv.conf:
-    /path/to/os/open.go:444
+    os.Open
+        /path/to/os/open.go:444
   - permission denied
 ```