Bump org.junit.jupiter:junit-jupiter in /modules/r2dbc

Bumps [org.junit.jupiter:junit-jupiter](https://github.com/junit-team/junit-framework) from 5.13.4 to 6.0.0.
- [Release notes](https://github.com/junit-team/junit-framework/releases)
- [Commits](junit-team/junit-framework@r5.13.4...r6.0.0)

---
updated-dependencies:
- dependency-name: org.junit.jupiter:junit-jupiter
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

modules/r2dbc/build.gradle

@@ -13,5 +13,5 @@ dependencies {
 
     testFixturesImplementation 'io.projectreactor:reactor-core:3.7.11'
     testFixturesImplementation 'org.assertj:assertj-core:3.27.6'
-    testFixturesImplementation 'org.junit.jupiter:junit-jupiter:5.13.4'
+    testFixturesImplementation 'org.junit.jupiter:junit-jupiter:6.0.0'
 }