Improve requiredAllExcept wording

Co-authored-by: Karen Etheridge <[email protected]>

Author: jdesrosiers

jsonschema-validation.xml

@@ -500,8 +500,8 @@
                     </t>
                     <t>
                         An object instance is valid against this keyword if every property name
-                        declared in "properties" except those that appear in the array is the name
-                        of a property in the instance.
+                        declared in "properties" is the name of a property in the instance, with
+                        the exception of the property names that appear in this keyword's array.
                     </t>
                 </section>