Fix CSS attributes to remove mismatched quote chars.

* Extra single/double quote chars are removed from css
  attributes in the sanitizer.
* This fixes parsing and rting of the snippet below extracted
  from the page en:List of miscellaneous works by Edward Blore
-----------
{|
!{{Grade II colour}}|II
|}
-----------
* No change in parser tests.

Change-Id: Ibd1dbeb5dd3e012de2c3cd290db7e2dd5b61a957
Merge "Fix CSS attributes to remove mismatched quote chars."