Fix link to graphiql

Author: menewman

docs/graphql/index.html

@@ -51,7 +51,7 @@ <h3>How can I test my queries during development?</h3>
                         <p>
                             Although you'll likely want to consume our API programmatically using a library in your language of choice,
                             as you work on your integration, you may find it helpful to have a readily available UI for writing and running queries.
-                            For that, try out our <a href="https://app.codesignal.com/graphql">GraphQL Playground</a>, which is connected to our real API
+                            For that, try out our <a href="https://app.codesignal.com/graphiql">GraphQL Playground</a>, which is connected to our real API
                             and provides a helpful interface that will make it easier for you to quickly spot and resolve syntax or schema issues in your queries.
                         </p>
                         <p>