Use samplesBranch=6.3.x

gradle.properties

@@ -1,6 +1,6 @@
 springBootVersion=3.1.1
 version=6.3.1-SNAPSHOT
-samplesBranch=main
+samplesBranch=6.3.x
 org.gradle.jvmargs=-Xmx3g -XX:+HeapDumpOnOutOfMemoryError
 org.gradle.parallel=true
 org.gradle.caching=true