Migrate dubbo-samples-async-generated-future-springboot to Spring Boot 3

- Bump spring-boot.version from 2.7.8 to 3.2.3
- Bump maven.compiler.source/target from 1.8 to 17 (required by Spring Boot 3)
- Correct unused spring.version property to 6.1.4 (was stale 4.3.30.RELEASE)
- Update case-versions.conf: dubbo.version=3.3.*, spring.version=6.*,
  java.version=[>= 17], so CI correctly scopes this module to the
  right Dubbo/Java test matrix

No javax.* -> jakarta.* changes needed; no source file in this module
references javax.* (the pom.xml's unused javax.annotation profile is
left untouched).

Verified: mvn clean install succeeds, and ConsumerApplicationTest passes
end-to-end against a live Zookeeper registry and Provider instance.

Author: Dhawaj Kumar Tomar

2-advanced/dubbo-samples-async/dubbo-samples-async-generated-future-springboot/case-versions.conf

@@ -20,6 +20,6 @@
 # Supported component versions of the test case
 
 # Spring app
-dubbo.version=2.7*, 3.*
-spring.version=4.*, 5.*
-java.version= [>= 8]
+dubbo.version=3.3.*
+spring.version=6.*
+java.version= [>= 17]

2-advanced/dubbo-samples-async/dubbo-samples-async-generated-future-springboot/pom.xml

@@ -37,13 +37,13 @@
     <description>Dubbo Samples Async Generated Future SpringBoot</description>
 
     <properties>
-        <maven.compiler.source>1.8</maven.compiler.source>
-        <maven.compiler.target>1.8</maven.compiler.target>
+        <maven.compiler.source>17</maven.compiler.source>
+        <maven.compiler.target>17</maven.compiler.target>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 
         <dubbo.version>3.3.1</dubbo.version>
-        <spring-boot.version>2.7.8</spring-boot.version>
-        <spring.version>4.3.30.RELEASE</spring.version>
+        <spring-boot.version>3.2.3</spring-boot.version>
+        <spring.version>6.1.4</spring.version>
         <junit.version>4.13.1</junit.version>
 
         <maven-compiler-plugin.version>3.7.0</maven-compiler-plugin.version>