[css-flexbox] fix typo

Author: tabatkins

css-flexbox/Overview.bs

@@ -2240,7 +2240,7 @@ Line Length Determination</h3>
 			<strong>Determine the available main and cross space for the flex items.</strong>
 			For each dimension,
 			if that dimension of the <a>flex container</a>’s content box is a <a>definite size</a>, use that;
-			if that dimension of the <a>flex container</a> is being sized under a <a lt="min-sizing constraint">min</a> or <a>max-sizing constraint</a>,
+			if that dimension of the <a>flex container</a> is being sized under a <a lt="min-content constraint">min</a> or <a>max-content constraint</a>,
 			the available space in that dimension is that constraint;
 			otherwise, subtract the <a>flex container</a>’s margin, border, and padding
 			from the space available to the flex container in that dimension