[Tech] Bump org.springframework.boot:spring-boot-starter-test

Bumps [org.springframework.boot:spring-boot-starter-test](https://github.com/spring-projects/spring-boot) from 3.1.5 to 3.2.4.
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v3.1.5...v3.2.4)

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

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

backend/build.gradle.kts

@@ -81,7 +81,7 @@ dependencies {
     testImplementation("io.ktor:ktor-client-mock-jvm:2.3.7")
     testImplementation("jakarta.servlet:jakarta.servlet-api:6.0.0")
     testImplementation("com.squareup.okhttp3:mockwebserver:4.10.0")
-    testImplementation("org.springframework.boot:spring-boot-starter-test:3.1.5")
+    testImplementation("org.springframework.boot:spring-boot-starter-test:3.2.4")
     testImplementation("org.springframework.restdocs:spring-restdocs-mockmvc:3.0.0")
     testImplementation("org.testcontainers:junit-jupiter:1.19.2")
     testImplementation("net.java.dev.jna:jna:5.13.0")