Fix Cowlib version in migration guide
diff --git a/doc/src/guide/migrating_from_2.1.asciidoc b/doc/src/guide/migrating_from_2.1.asciidoc
index 0cd2f43..3cacc9e 100644
--- a/doc/src/guide/migrating_from_2.1.asciidoc
+++ b/doc/src/guide/migrating_from_2.1.asciidoc
@@ -25,7 +25,7 @@
 * The `state_name`, `event_handler` and `event_handler_state`
   fields were added to `gun:info/1`.
 
-* Update Cowlib to 2.14.1.
+* Update Cowlib to 2.15.0.
 
 === Experimental features added