Fix CHANGELOG tense

Author: TheBolliwood

juniper_warp/CHANGELOG.md

@@ -7,7 +7,7 @@
 - Update `playground_filter` to support subscription endpoint URLs
 - Update `warp` to 0.2
 - Rename synchronous `execute` to `execute_sync`, add asynchronous `execute`
-- Added `graphql_subscriptions` on_connect handler
+- Add `graphql_subscriptions` on_connect handler
 
 # [[0.5.2] 2019-12-16](https://github.com/graphql-rust/juniper/releases/tag/juniper_warp-0.5.2)