build(deps): bump io.projectreactor:reactor-test from 3.5.11 to 3.8.4

Bumps [io.projectreactor:reactor-test](https://github.com/reactor/reactor-core) from 3.5.11 to 3.8.4.
- [Release notes](https://github.com/reactor/reactor-core/releases)
- [Commits](reactor/reactor-core@v3.5.11...v3.8.4)

---
updated-dependencies:
- dependency-name: io.projectreactor:reactor-test
  dependency-version: 3.8.4
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

rest/build.gradle

@@ -9,5 +9,5 @@ dependencies {
     implementation "io.projectreactor.netty:reactor-netty-http:${revReactor}"
     implementation "org.springdoc:springdoc-openapi-starter-webmvc-ui:${revSpringDoc}"
 
-    testImplementation "io.projectreactor:reactor-test:3.5.11"
+    testImplementation "io.projectreactor:reactor-test:3.8.4"
 }