Incorporate suggested change

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

Author: gregsdennis

jsonschema-core.xml

@@ -2430,7 +2430,7 @@
                         </t>
                         <t>
                             The annotation result of this keyword is the set of instance
-                            property names matched by at least one key in this keyword.
+                            property names matched by at least one property under this keyword.
                             This annotation affects the behavior of "additionalProperties" (in this
                             vocabulary) and "unevaluatedProperties" (in the Unevaluated vocabulary).
                         </t>