Start building against Spring Framework 6.1.6 snapshots

See gh-40225

Author: wilkinsona

gradle.properties

@@ -14,7 +14,7 @@ junitJupiterVersion=5.10.2
 kotlinVersion=1.9.23
 mavenVersion=3.9.4
 nativeBuildToolsVersion=0.10.1
-springFrameworkVersion=6.1.5
+springFrameworkVersion=6.1.6-SNAPSHOT
 tomcatVersion=10.1.19
 snakeYamlVersion=2.2