[css-flexbox-1] align wording

See #7768 (comment)

Author: fantasai

css-flexbox-1/Overview.bs

@@ -613,9 +613,9 @@ Flex Items</h2>
 
 	Each in-flow child of a <a>flex container</a>
 	becomes a <a>flex item</a>,
-	and each contiguous sequence of child <a>text sequences</a>
+	and each child <a>text sequence</a>
 	is wrapped in an <a>anonymous</a> <a>block container</a> <a>flex item</a>.
-	However, if the entire sequence of child <a>text sequences</a> contains only
+	However, if the entire <a>text sequences</a> contains only
 	[=document white space characters=]
 	(i.e. characters that can be affected by the 'white-space' property)
 	it is instead not rendered (just as if its <a>text nodes</a> were ''display:none'').