Update spring core to v5.3.21 (#12582)

Co-authored-by: Renovate Bot <[email protected]>

Author: renovate[bot]

gradle.properties

@@ -39,7 +39,7 @@ slf4jVersion=1.7.36
 spockVersion=2.1-groovy-3.0
 springBootVersion=2.7.0
 springLoadedVersion=1.2.8.RELEASE
-springVersion=5.3.20
+springVersion=5.3.21
 testingSupportVersion=2.4.1
 testingSupportVersionForTests=2.6.1
 tomcatLog4jVersion=8.5.2