GH-198 - Upgrade to Spring Boot 3.1 snapshots.

Switch verification of mock beans as Mockito 5.3.0 uses a different MockMaker by default that doesn't add the explicit interface we have previously checked for.

Remove obsolete init- and destroy method declarations from service bean definitions in examples.

spring-modulith-examples/pom.xml

@@ -4,7 +4,7 @@
 	<parent>
 		<groupId>org.springframework.boot</groupId>
 		<artifactId>spring-boot-starter-parent</artifactId>
-		<version>3.1.0-RC1</version>
+		<version>3.1.0-SNAPSHOT</version>
 		<relativePath />
 	</parent>