Give the example placeholder its own line-height.

This way it doesn't inherit from something further up, whose line-height
may be more or less than we expect.

examples/examples.css

@@ -89,7 +89,7 @@ input[type=checkbox] {
 	width: 100%;
 	height: 100%;
 	font-size: 14px;
-	line-height: 14px;
+	line-height: 1.2em;
 }
 
 .legend table {