Update dependency ch.qos.logback:logback-classic to v1.5.21 (#64)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

gradle/libs.versions.toml

@@ -2,7 +2,7 @@
 hivemq-mqttClient = "1.3.10"
 jetbrains-annotations = "26.0.2-1"
 junit-jupiter = "5.10.2"
-logback = "1.5.20"
+logback = "1.5.21"
 mockito = "5.20.0"
 testcontainers = "1.21.3"