fix link

Author: lindseymoore

source/index.txt

@@ -26,7 +26,7 @@
    /compatibility
    Validate Driver Artifact Signatures </validate-signatures>
    View the Source <https://github.com/mongodb/mongo-java-driver/tree/master/driver-kotlin-sync>
-   API Documentation <{+api+}>
+   API Documentation <{+api+}/com.mongodb.kotlin.client/index.html>
 
 Introduction
 ------------