Some third-party.rst cleanup

The third-party.rst file has encountered a few changes over the
last months. This patch cleans up some grammar, updates the
lines of expected communication should an account be disabled
and generally tries to bring some uniformity to the file.

No significant changes in meaning are intended, just cosmetic
edits.

Change-Id: I0c59d93721df35e7ea90c870cad230fb2a38010d
Merge "Some third-party.rst cleanup"