docs: update readme to point client libarary documentation (#317)

Author: suraj-qlogic

README.md

@@ -248,7 +248,7 @@ Java 8 Windows | [![Kokoro CI][kokoro-badge-image-4]][kokoro-badge-link-4]
 Java 11 | [![Kokoro CI][kokoro-badge-image-5]][kokoro-badge-link-5]
 
 [product-docs]: https://cloud.google.com/storage
-[javadocs]: https://googleapis.dev/java/java-storage/latest/
+[javadocs]: https://googleapis.dev/java/google-cloud-storage/latest/index.html
 [kokoro-badge-image-1]: http://storage.googleapis.com/cloud-devrel-public/java/badges/java-storage/java7.svg
 [kokoro-badge-link-1]: http://storage.googleapis.com/cloud-devrel-public/java/badges/java-storage/java7.html
 [kokoro-badge-image-2]: http://storage.googleapis.com/cloud-devrel-public/java/badges/java-storage/java8.svg