Update dependency org.testcontainers:testcontainers-bom to v1.21.0

Author: renovate[bot]

gradle/libs.versions.toml

@@ -6,7 +6,7 @@ junit = "5.11.4"
 logback = "1.5.15"
 postgresql = "42.7.4"
 tap4j = "4.4.2"
-testcontainers = "1.20.4"
+testcontainers = "1.21.0"
 
 [libraries]
 flywayCore = { module = "org.flywaydb:flyway-core", version.ref = "flyway" }