Fix link to IdString in 2.14.13 release notes

The link was copied from the 2.15 release notes, where the change
was originally released, and links to the stable-2.15 version of
the code.

Change it to stable-2.14.

Change-Id: I021383ce65dcc00748e7ae519eb1d1b4be2bf547
diff --git a/pages/site/releases/2.14.md b/pages/site/releases/2.14.md
index ee9e44f..b599c04 100644
--- a/pages/site/releases/2.14.md
+++ b/pages/site/releases/2.14.md
@@ -333,7 +333,7 @@
 
 ### 2.14.13
 
-* Instances of [IdString](https://gerrit.googlesource.com/gerrit/+/stable-2.15/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/IdString.java)
+* Instances of [IdString](https://gerrit.googlesource.com/gerrit/+/stable-2.14/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/IdString.java)
   used to return true when `equals` was given a String instance equal to the
   IdString's URL-encoded value. This violates
   [symmetry](https://en.wikipedia.org/wiki/Equivalence_relation#Definition), so