[ Reason ]
Thunderbird will come with a new version (>=153.4) into stable. This need an
update for the Add-Ons (here: allow-html-temp) too.

[ Impact ]
If the update isn't approved the user can't anymore use it
in recent thunderbird.

[ Tests ]
The same upstream code works with thunderbird >= 153.4 in testing.

[ Risks ]
Code is trivial so no risk.

[ Checklist ]
  [X] *all* changes are documented in the d/changelog
  [X] I reviewed all changes and I approve them
  [X] attach debdiff against the package in (old)stable
  [X] the issue is verified as fixed in unstable

[ Changes ]
The new version of thunderbird needs a new version of webext-allow-html-temp.

[ Other info ]
The only reason is the new upcoming version of the thunderbird.

With the proposed update we should wait until the (security-) update of
Thunderbird to 153.x.