Bump org.springframework:spring-framework-bom from 6.1.14 to 6.1.15

Bumps [org.springframework:spring-framework-bom](https://github.com/spring-projects/spring-framework) from 6.1.14 to 6.1.15.
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](spring-projects/spring-framework@v6.1.14...v6.1.15)

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

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

gradle/libs.versions.toml

@@ -13,7 +13,7 @@ org-jetbrains-kotlin = "1.9.25"
 org-jetbrains-kotlinx = "1.8.1"
 org-mockito = "5.11.0"
 org-opensaml = "4.3.2"
-org-springframework = "6.1.14"
+org-springframework = "6.1.15"
 
 [libraries]
 ch-qos-logback-logback-classic = "ch.qos.logback:logback-classic:1.5.12"