[selectors-4][css-pseudo-4] Revert placeholder option example, since HTML doesn't include it atm. #2517

Author: fantasai

css-pseudo-4/Overview.bs

@@ -1189,8 +1189,7 @@ Placeholder Input: the ''::placeholder'' pseudo-element</h3>
   <div class="example">
     For example, according to the semantics of [[HTML]]
     the <{input/placeholder}> attribute on the <{input}> and <{textarea}> elements
-    provide placeholder text,
-    as does the first <{option}> element of a <{select}> under certain conditions.
+    provide placeholder text.
     The ''::placeholder'' [=pseudo-element=]
     represents such text when it is displayed.
   </div>

selectors-4/Overview.bs

@@ -2660,8 +2660,7 @@ The Placeholder-shown Pseudo-class: '':placeholder-shown''</h4>
 	<div class="example">
 		For example, according to the semantics of [[HTML]]
 		the <{input/placeholder}> attribute on the <{input}> and <{textarea}> elements
-		provide placeholder text,
-		as does the first <{option}> element of a <{select}> under certain conditions.
+		provide placeholder text.
 		The '':placeholder-shown'' class thus applies
 		whenever such placeholder text is shown.
 	</div>