Bump io.micronaut.platform:micronaut-platform in /reactive/micronaut

Bumps [io.micronaut.platform:micronaut-platform](https://github.com/micronaut-projects/micronaut-platform) from 4.8.3 to 4.9.0.
- [Release notes](https://github.com/micronaut-projects/micronaut-platform/releases)
- [Commits](micronaut-projects/micronaut-platform@v4.8.3...v4.9.0)

---
updated-dependencies:
- dependency-name: io.micronaut.platform:micronaut-platform
  dependency-version: 4.9.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

reactive/micronaut/build.gradle.kts

@@ -20,7 +20,7 @@ dependencies {
     compileOnly("io.micronaut:micronaut-http-client")
     runtimeOnly("ch.qos.logback:logback-classic")
     testImplementation("io.micronaut:micronaut-http-client")
-    aotPlugins(platform("io.micronaut.platform:micronaut-platform:4.8.3"))
+    aotPlugins(platform("io.micronaut.platform:micronaut-platform:4.9.0"))
     aotPlugins("io.micronaut.security:micronaut-security-aot")
 }