[fix] make /preferences more CSP compliant - simple & oscar theme

In simple & oscar theme remove ``style=`` properties which violates CSP but seem
not to have a magnification in GUI (UX).

Fixed files::

    ./oscar/preferences.html:25:<td class="{{ label }}" style="padding: 2px">{{- "" -}}
    ./simple/preferences.html:39:<td class="{{ label }}" style="padding: 2px; width: 13rem;">{{- "" -}}
    ./simple/preferences.html:77:    <div class="engine-tooltip" style="right: 12rem;" role="tooltip" id="{{engine_name}}_reliability">
    ./simple/preferences.html:258:     <p class="text-muted" style="margin:20px 0;">

Reported-by: https://github.com/searxng/searxng/issues/57


Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>