fix link to API doc (#247)

Author: Chris Cho

source/upgrade.txt

@@ -57,7 +57,7 @@ Version 4.7 Breaking Changes
 
 - The ``setWindowFields`` builder API is no longer beta. The new builder
   breaks binary and source compatibility. See the
-  `Aggregates API documentation https://mongodb.github.io/mongo-java-driver/4.7/apidocs/mongodb-driver-core/com/mongodb/client/model/Aggregates.html>`__
+  `Aggregates API documentation <https://mongodb.github.io/mongo-java-driver/4.7/apidocs/mongodb-driver-core/com/mongodb/client/model/Aggregates.html>`__
   for information the new ``setWindowFields()`` method signatures.
 
   If your application uses this builder in a version prior to v4.7, update