Update logback monorepo to v1.5.21 (#525)

Author: renovate[bot]

gradle/libs.versions.toml

@@ -11,7 +11,7 @@ retrofit = "3.0.0"
 kotlin-coroutines = "1.10.2"
 kotlin-binary-compatibility-validator = "0.18.1"
 slf4j = "2.0.17"
-logback = "1.5.20"
+logback = "1.5.21"
 guava = "33.5.0-jre"
 maven-publish-plugin = "0.34.0"