Don't set colour of SVG elements

Instead set the default colour on the body element so that it will be
inherited

themes/tiddlywiki/vanilla/base.tid

@@ -71,6 +71,7 @@ body.tc-body {
 	line-height: {{$:/themes/tiddlywiki/vanilla/metrics/lineheight}};
 	color: <<colour foreground>>;
 	background-color: <<colour page-background>>;
+	fill: <<colour foreground>>;
 	word-wrap: break-word;
 	<<custom-background-datauri>>
 }
@@ -130,10 +131,6 @@ input:not([type]) {
 	color: <<colour muted-foreground>>;
 }
 
-svg {
-	fill: <<colour foreground>>;
-}
-
 svg.tc-image-button {
 	padding: 0px 1px 1px 0px;
 }