Bump org.springframework.boot:spring-boot-starter-parent in /backend

Bumps [org.springframework.boot:spring-boot-starter-parent](https://github.com/spring-projects/spring-boot) from 3.1.1 to 3.1.3.
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v3.1.1...v3.1.3)

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

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

Author: dependabot[bot]

backend/auth-service/pom.xml

@@ -9,7 +9,7 @@
     <parent>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-parent</artifactId>
-        <version>3.1.1</version>
+        <version>3.1.3</version>
         <relativePath />
     </parent>