fix: add the okhttpclient page to rapid tree (#245)

Author: dtayeh

docs/tree.yml

@@ -11,4 +11,5 @@ children:
   - path: products/rapid/sdk/java/exception-handling.md
   - path: products/rapid/sdk/java/transitioning-to-v4-1-0.md
   - path: products/rapid/sdk/java/links.md
+  - path: products/rapid/sdk/java/okhttpclient.md
   - path: products/rapid/sdk/java/reference.md