docs: Updated link, wording associated with data-sharing IPC.

A paragraph under the "Requesting Permissions" section of the
"Security Tips" page discusses the complications associated with
sharing data over inter-process communication (IPC) when the clients
involved have different permission settings. This paragraph now
includes a working link and clearer wording to describe the concept.

Bug: 26807597
Change-Id: I35e316f5f97d4ec45d9beaae95424221e6a92da5