Bump Spring Boot to 3.0.0-RC2 (#2692)

#### What type of PR is this?

/kind improvement
/area core
/milestone 2.0

#### What this PR does / why we need it:

Bump Spring Boot to 3.0.0-RC2. 

See https://github.com/spring-projects/spring-boot/releases/tag/v3.0.0-RC2 for more.

#### Does this PR introduce a user-facing change?

```release-note
升级 Spring Boot 至 3.0.0-RC2
```

build.gradle

@@ -1,5 +1,5 @@
 plugins {
-    id 'org.springframework.boot' version '3.0.0-RC1'
+    id 'org.springframework.boot' version '3.0.0-RC2'
     id 'io.spring.dependency-management' version '1.1.0'
     id "checkstyle"
     id 'java'