Bump org.springframework:spring-framework-bom from 6.1.20 to 6.1.21

Bumps [org.springframework:spring-framework-bom](https://github.com/spring-projects/spring-framework) from 6.1.20 to 6.1.21.
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](spring-projects/spring-framework@v6.1.20...v6.1.21)

---
updated-dependencies:
- dependency-name: org.springframework:spring-framework-bom
  dependency-version: 6.1.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -12,7 +12,7 @@ protobuf = "3.25.8"
 pulsar = "3.2.4"
 pulsar-reactive = "0.5.10"
 reactor = "2023.0.19"
-spring = "6.1.20"
+spring = "6.1.21"
 # tests
 assertj = "3.27.3"
 awaitility = "4.3.0"