Update all minor dependencies to v1.21.0

Author: renovate[bot]

gradle/libs.versions.toml

@@ -11,7 +11,7 @@ junit-jupiter = "5.10.3"
 logback = "1.5.18"
 mockito = "5.17.0"
 okhttp = "4.12.0"
-testcontainers = "1.20.6"
+testcontainers = "1.21.0"
 
 [libraries]
 awaitility = { module = "org.awaitility:awaitility", version.ref = "awaitility" }