Merge pull request #1601 from grails/renovate/spring-core

Update spring core to v5.3.15

Author: puneetbehl

gradle.properties

@@ -13,7 +13,7 @@ commonsValidatorVersion=1.7
 hibernateVersion=5.6.3.Final
 servletApiVersion=4.0.1
 spockVersion=2.0-groovy-3.0
-springVersion=5.3.14
+springVersion=5.3.15
 caffeineVersion=2.9.3
 grailsVersion=5.1.1
 grailsAsyncVersion=4.0.0