dependency: (deps): bump io.spring.dependency-management in /backend

Bumps [io.spring.dependency-management](https://github.com/spring-gradle-plugins/dependency-management-plugin) from 1.1.5 to 1.1.6.
- [Release notes](https://github.com/spring-gradle-plugins/dependency-management-plugin/releases)
- [Commits](spring-gradle-plugins/dependency-management-plugin@v1.1.5...v1.1.6)

---
updated-dependencies:
- dependency-name: io.spring.dependency-management
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

backend/build.gradle.kts

@@ -2,7 +2,7 @@ plugins {
 	java
 	jacoco
 	id("org.springframework.boot") version "3.3.1"
-	id("io.spring.dependency-management") version "1.1.5"
+	id("io.spring.dependency-management") version "1.1.6"
 	id("com.github.roroche.plantuml") version "1.0.2"
 }