[solarized theme] Remove tab background character

It doesn't belong in a theme.

theme/solarized.css

@@ -88,11 +88,6 @@ http://ethanschoonover.com/solarized/img/solarized-palette.png
   text-decoration-style: dotted;
 }
 .cm-s-solarized .cm-strong { color: #eee; }
-.cm-s-solarized .cm-tab:before {
-  content: "➤";   /*visualize tab character*/
-  color: #586e75;
-  position:absolute;
-}
 .cm-s-solarized .cm-error,
 .cm-s-solarized .cm-invalidchar {
   color: #586e75;