Bump io.projectreactor.netty:reactor-netty from 1.1.18 to 1.1.21

Bumps [io.projectreactor.netty:reactor-netty](https://github.com/reactor/reactor-netty) from 1.1.18 to 1.1.21.
- [Release notes](https://github.com/reactor/reactor-netty/releases)
- [Commits](reactor/reactor-netty@v1.1.18...v1.1.21)

---
updated-dependencies:
- dependency-name: io.projectreactor.netty:reactor-netty
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

gradle/libs.versions.toml

@@ -16,7 +16,7 @@ jackson-module-kotlin = { module = "com.fasterxml.jackson.module:jackson-module-
 jackson-datatype-jsr310 = { module = "com.fasterxml.jackson.datatype:jackson-datatype-jsr310", version.ref = "jackson" }
 guava = { module = "com.google.guava:guava", version = "33.2.0-jre" }
 reactor-core = { module = "io.projectreactor:reactor-core", version.ref = "reactor" }
-reactor-netty = { module = "io.projectreactor.netty:reactor-netty", version = "1.1.18" }
+reactor-netty = { module = "io.projectreactor.netty:reactor-netty", version = "1.1.21" }
 luaj-jse = { module = "org.luaj:luaj-jse", version = "3.0.1" }
 zstd-jni = { module = "com.github.luben:zstd-jni", version = "1.5.2-5" } # >=1.5.4-1 fails
 commons-compress = { module = "org.apache.commons:commons-compress", version = "1.26.1" }