Start building against Spring Framework 6.1.9 snapshots

See gh-41034

Author: wilkinsona

gradle.properties

@@ -14,7 +14,7 @@ junitJupiterVersion=5.10.2
 kotlinVersion=1.9.24
 mavenVersion=3.9.4
 nativeBuildToolsVersion=0.10.2
-springFrameworkVersion=6.1.8
+springFrameworkVersion=6.1.9-SNAPSHOT
 springFramework60xVersion=6.0.21
 tomcatVersion=10.1.24
 snakeYamlVersion=2.2