Change samplesBranch property to point to correct branch

Closes gh-11040

gradle.properties

@@ -5,7 +5,7 @@ springFrameworkVersion=5.3.17
 openSamlVersion=3.4.6
 version=5.7.0-SNAPSHOT
 kotlinVersion=1.6.20-RC
-samplesBranch=main
+samplesBranch=5.7.x
 org.gradle.jvmargs=-Xmx3g -XX:MaxPermSize=2048m -XX:+HeapDumpOnOutOfMemoryError
 org.gradle.parallel=true
 org.gradle.caching=true