[css-overflow] Write ::first-letter with 2 colons in one place it wasn't.

Author: dbaron

css-overflow/Overview.bs

@@ -860,7 +860,7 @@ rather than just one page at once?</p>
 	<p class="issue">
 		This inheritance rule allows specifying styles indirectly
 		(by using explicit ''inherit'' or using default inheritance
-		on properties that don't apply to '':first-letter'')
+		on properties that don't apply to ''::first-letter'')
 		that can't be specified directly
 		(based on the rules in the next section).
 		This is a problem.

css-overflow/Overview.html

@@ -1288,10 +1288,10 @@ <h4 class="heading settled" data-level="6.1.2" id="style-of-fragments"><span cla
 	</p>
 
 
-   <p class="issue" id="issue-5862943f"><a class="self-link" href="#issue-5862943f"></a>
+   <p class="issue" id="issue-20d2a9e8"><a class="self-link" href="#issue-20d2a9e8"></a>
 		This inheritance rule allows specifying styles indirectly
 		(by using explicit <a class="css" data-link-type="maybe" href="http://dev.w3.org/csswg/css-cascade-3/#valuedef-inherit">inherit</a> or using default inheritance
-		on properties that don’t apply to <span class="css">:first-letter</span>)
+		on properties that don’t apply to <span class="css">::first-letter</span>)
 		that can’t be specified directly
 		(based on the rules in the next section).
 		This is a problem.
@@ -2124,13 +2124,13 @@ <h2 class="no-num heading settled" id="issues-index"><span class="content">Issue
    <div class="issue">
 		This inheritance rule allows specifying styles indirectly
 		(by using explicit <a class="css" data-link-type="maybe" href="http://dev.w3.org/csswg/css-cascade-3/#valuedef-inherit">inherit</a> or using default inheritance
-		on properties that don’t apply to <span class="css">:first-letter</span>)
+		on properties that don’t apply to <span class="css">::first-letter</span>)
 		that can’t be specified directly
 		(based on the rules in the next section).
 		This is a problem.
 		The restrictions that apply to styling inside fragments
 		should also apply to inheritance from fragments.
-	<a href="#issue-5862943f"> ↵ </a></div>
+	<a href="#issue-20d2a9e8"> ↵ </a></div>
    <div class="issue">
 		Should this apply to fragment overflow only,
 		or also to paginated overflow,