Bump org.springframework.boot:spring-boot-gradle-plugin

Bumps [org.springframework.boot:spring-boot-gradle-plugin](https://github.com/spring-projects/spring-boot) from 2.7.5 to 3.1.0.
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v2.7.5...v3.1.0)

---
updated-dependencies:
- dependency-name: org.springframework.boot:spring-boot-gradle-plugin
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

webflux/build.gradle

@@ -1,6 +1,6 @@
 buildscript {
 	ext {
-		springBootVersion = '2.7.5'
+		springBootVersion = '3.1.0'
 	}
 	repositories {
 		mavenCentral()