Update dependency org.testcontainers:postgresql to v1.21.0

Author: renovate[bot]

postgres-cdc/build.gradle

@@ -17,7 +17,7 @@ testing {
     suites {
         test {
             dependencies {
-                implementation("org.testcontainers:postgresql:1.20.4")
+                implementation("org.testcontainers:postgresql:1.21.0")
                 implementation("org.assertj:assertj-core:3.26.3")
                 implementation("org.flywaydb:flyway-core:9.22.3")
                 implementation("org.awaitility:awaitility:4.2.2")