[css-break-3] s/can/will/ per astearns' suggestion

Author: fantasai

css-break-3/Overview.bs

@@ -799,7 +799,7 @@ Optimizing Unforced Breaks</h3>
   must appear on the earlier side of a <a>fragmentation break</a>
   if it is able to fit within the <a>fragmentainer</a>.
 
-  Note: A zero-sized <a>box fragment</a> can be pushed
+  Note: A zero-sized <a>box fragment</a> will be pushed
   to the next <a>fragmentainer</a>
   if it is placed immediately after content
   that itself overflows the <a>fragmentainer</a>.