[css-align] as the fallback for -> the fallback of for clarity #1432

Author: fantasai

css-align/Overview.bs

@@ -1150,7 +1150,7 @@ Inline/Main-Axis Alignment: the 'justify-self' property</h3>
 			<th>''justify-self/normal'' Behavior
 			<td>
 				Behaves as ''flex-start''
-				(as the fallback for ''justify-self/stretch'' for fixed-size boxes).
+				(the fallback of ''justify-self/stretch'' for fixed-size boxes).
 	</table>
 
 ### Table Cells ### {#justify-cell}
@@ -1346,7 +1346,7 @@ Block/Cross-Axis Alignment: the 'align-self' property</h3>
 			<th>''align-self/normal'' Behavior
 			<td>
 				Behaves as ''flex-start''
-				(as the fallback for ''align-self/stretch'' for fixed-size boxes).
+				(the fallback of ''align-self/stretch'' for fixed-size boxes).
 	</table>
 
 ### Table Cells ### {#align-cell}