[css-sizing] Apply dholbert's suggested edit. Also grammar/markup fixes. Fixes #2128.

Author: tabatkins

css-sizing-3/Overview.bs

@@ -705,21 +705,20 @@ Intrinsic Size Determination</h2>
 Intrinsic Sizes</h3>
 
 	The <a>min-content size</a> of a box in each axis
-	is the size it would have if it were
+	is the size it would have if it was
 	a float given an ''width/auto'' size in that axis
 	(and no <a lt="min size">minimum</a> or <a>maximum size</a> in that axis)
-	and whose containing block was <em>zero</em>-sized in that axis.
+	and if its containing block was <em>zero</em>-sized in that axis.
 	(In other words, the minimum size it has when sized as “shrink-to-fit”.)
 
 	The <a>max-content size</a> of a box in each axis
-	is the size it would have if it were
+	is the size it would have if it was
 	a float given an ''width/auto'' size in that axis
 	(and no <a lt="min size">minimum</a> or <a>maximum size</a> in that axis),
-	and whose containing block was <em>infinitely</em>-sized in that axis.
+	and if its containing block was <em>infinitely</em>-sized in that axis.
 	(In other words, the maximum size it has when sized as “shrink-to-fit”.)
 
-	<p class="note">
-	Note that when the box has an intrinsic aspect ratio,
+	Note: Note that when the box has an intrinsic aspect ratio,
 	size constraints in the opposite dimension will transfer through
 	and can affect the ''width/auto'' size in the considered one.
 	See <a href="https://www.w3.org/TR/CSS2/visudet.html">CSS2&sect;10</a>.