3.1.x: Bump org.springframework.boot:spring-boot-dependencies

Bumps [org.springframework.boot:spring-boot-dependencies](https://github.com/spring-projects/spring-boot) from 3.1.3 to 3.1.9.
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v3.1.3...v3.1.9)

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

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

build.gradle

@@ -24,7 +24,7 @@ description = "Spring CredHub"
 
 ext {
 	springVersion = "6.0.11"
-	springBootVersion = "3.1.3"
+	springBootVersion = "3.1.9"
 	springSecurityVersion = "6.1.2"
 	javadocLinks = [
 			"https://docs.oracle.com/en/java/javase/17/docs/api/",