Upgrade to Spring Framework 6.0.0-M2

Closes gh-10706

gradle.properties

@@ -1,7 +1,7 @@
 aspectjVersion=1.9.8.RC3
 springJavaformatVersion=0.0.29
 springBootVersion=2.4.2
-springFrameworkVersion=6.0.0-M1
+springFrameworkVersion=6.0.0-M2
 openSamlVersion=3.4.6
 version=6.0.0-SNAPSHOT
 kotlinVersion=1.6.10