[Fix] oscar: no HTML escaping prior to output

When results are fetched from any programming related documentation site
(like git-scm.com, docs.python.org etc), content in Info box is shown as
raw HTML code.

This change addresses the issue by using "safe" filter feature provided by
Django. See,
  - https://docs.djangoproject.com/en/3.0/ref/templates/builtins/#safe
  - Searx issue tracker (issue #1649), for more information.

Resolves: #1649