[FLINK-39099] Update testcontainers to fix GitHub runner Docker compatibility issue

Co-authored-by: Aleksandr Savonin <savonitar@gmail.com>

Author: ferenc-csaky

pom.xml

@@ -164,7 +164,7 @@ under the License.
 		<beam.version>2.54.0</beam.version>
 		<protoc.version>4.32.1</protoc.version>
 		<okhttp.version>3.14.9</okhttp.version>
-		<testcontainers.version>1.20.2</testcontainers.version>
+		<testcontainers.version>1.21.4</testcontainers.version>
 		<lz4.version>1.8.0</lz4.version>
 		<commons.io.version>2.15.1</commons.io.version>
 		<japicmp.skip>false</japicmp.skip>