Update dependency org.openjdk.nashorn:nashorn-core to v15.7

Author: renovate[bot]

pom.xml

@@ -120,7 +120,7 @@
     <dependency>
       <groupId>org.openjdk.nashorn</groupId>
       <artifactId>nashorn-core</artifactId>
-      <version>15.6</version>
+      <version>15.7</version>
       <scope>test</scope>
     </dependency>
   </dependencies>