Update bson-type-comparison-order.txt

Author: bagratte

source/reference/bson-type-comparison-order.txt

@@ -82,7 +82,7 @@ Dates and Timestamps
 Non-existent Fields
 -------------------
 
-The comparison treats a non-existent field as it would an empty BSON
+The comparison treats a non-existent field as if it were an empty BSON
 Object. As such, a sort on the ``a`` field in documents ``{ }`` and ``{
 a: null }`` would treat the documents as equivalent in sort order.