SPARK-1135: fix broken anchors in docs

A recent PR that added Java vs Scala tabs for streaming also
inadvertently added some bad code to a document.ready handler, breaking
our other handler that manages scrolling to anchors correctly with the
floating top bar. As a result the section title ended up always being
hidden below the top bar. This removes the unnecessary JavaScript code.

Author: Matei Zaharia <matei@databricks.com>

Closes #3 from mateiz/doc-links and squashes the following commits:

e2a3488 [Matei Zaharia] SPARK-1135: fix broken anchors in docs