bug#34976: [debbugs.el] debbugs-read-emacs-bug-with-gnus sets user options

[Basil L. Contovounesios]

X-Debbugs-Cc: Lars Ingebrigtsen <larsi@gnus.org>, Michael Albinus 
<michael.albinus@gmx.de>, Noam Postavsky <npostavs@gmail.com>

When I use Gnus as my MUA, I leave the user options
gnus-suppress-duplicates and gnus-save-duplicate-list at their default
value of nil, as I have not yet run into any issues with duplicate
messages.

After using debbugs.el, however, I noticed that the value of these two
user options had been changed, and a file called 'suppression' had
appeared under my gnus-directory.  I think this was caused by a change
to debbugs-read-emacs-bug-with-gnus[1].

[1]: Save list of read articles
  2015-12-26 01:17:29 +0100
  
https://git.savannah.gnu.org/cgit/emacs/elpa.git/commit/?id=f43413e5ad2817fb0ee055e358178924a6affe8b

I don't know what sort of issues gave rise to this change, but it would
be nice if debbugs.el could do its job without permanently changing the
value of user options from other packages.

Thanks,

-- 
Basil

In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, X toolkit, Xaw3d scroll 
bars)
 of 2019-03-24 built on thunk
Repository revision: dbd6490ad49b0f088d56cdd5f04178bdd62c806a
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12003000
System Description: Debian GNU/Linux buster/sid