[css-flexbox] Revert removal of flex factor floor in intrinsic sizing section (see changeset 16063:5a9bb0bc0ef0)

Author: fantasai

css-flexbox/Overview.bs

@@ -2716,10 +2716,9 @@ Intrinsic Sizes</h3>
 		<li>
 			For each <a>flex item</a>,
 			subtract its outer <a>flex base size</a> from its <a>max-content contribution</a> size.
-			If that result is not zero, divide it by its <a>flex grow factor</a> (if the result was positive)
-			or by its <a>scaled flex shrink factor</a> (if the result was negative).
+			If that result is not zero, divide it by (if the result was positive) its <a>flex grow factor</a> floored at 1,
+			or (if the result was negative) by its <a>scaled flex shrink factor</a>, having floored the <a>flex shrink factor</a> at 1.
 			This is the item's <var>max-content flex fraction</var>.
-
 		<li>
 			Place all <a>flex items</a> into lines of infinite length.