lisp/ox-html.el: Fix `org-html-style-default'

* lisp/ox-html.el (org-html-style-default): Remove faulty .org-svg css
class specifications.

Reported-by: Yuchen Guo <Guoyuc@students.uni-marburg.de>

lisp/ox-html.el

@@ -442,7 +442,7 @@ property on the headline itself.")
     { font-size: 10px; font-weight: bold; white-space: nowrap; }
   .org-info-js_search-highlight
     { background-color: #ffff00; color: #000000; font-weight: bold; }
-  .org-svg { width: 90%; }
+  .org-svg { }
 </style>"
   "The default style specification for exported HTML files.
 You can use `org-html-head' and `org-html-head-extra' to add to