Faulty SVG width in default HTML export style

[Yuchen Guo]

Currently the style specified for SVG images
in `org-html-style-default' variable is the following:

    .org-svg { width: 90%; }

This causes a single image (math formula) to occupy almost the width of
the entire page, rendering the page unreadable.

In my experiment removing this line fixed the issue.

Two PNG screenshots demostrating the issue is available under the
following links:

https://w.wiki/4uQd
https://w.wiki/4uQe

-- 
Yuchen Guo