[css-display-3] Fix indentation

Author: fantasai

css-display-3/Overview.bs

@@ -43,13 +43,13 @@ spec:css-pseudo-4; type:selector;
 	text: ::before
 	text: ::after
 spec: svg2;
-    type:dfn;
-        text: container element
-        text: text content child element
-        text: renderable element
-        text: non-rendered element
-        text: rendered element
-        text: presentation attribute
+	type:dfn;
+		text: container element
+		text: text content child element
+		text: renderable element
+		text: non-rendered element
+		text: rendered element
+		text: presentation attribute
 </pre>
 
 <style>