Bump dataflowLegacyContainerVersion (apache#29723)

Author: Abacn

runners/google-cloud-dataflow-java/build.gradle

@@ -51,7 +51,7 @@ evaluationDependsOn(":sdks:java:container:java11")
 
 ext.dataflowLegacyEnvironmentMajorVersion = '8'
 ext.dataflowFnapiEnvironmentMajorVersion = '8'
-ext.dataflowLegacyContainerVersion = 'beam-master-20231026'
+ext.dataflowLegacyContainerVersion = 'beam-master-20231212'
 ext.dataflowFnapiContainerVersion = 'beam-master-20231026'
 ext.dataflowContainerBaseRepository = 'gcr.io/cloud-dataflow/v1beta3'