docs: staging/tee.rst: convert into definition list

Fix the following warnings:

tee.rst:65: WARNING: Unexpected indentation.

tee.rst:69: WARNING: Block quote ends without a
blank line; unexpected unindent.

By switching to the 'definition list' syntax.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
Link: https://lore.kernel.org/r/20200718165107.625847-4-dwlsalmeida@gmail.com


Signed-off-by: Jonathan Corbet <corbet@lwn.net>