[BEAM-12231] Bump Dataflow container version (#14733)

diff --git a/runners/google-cloud-dataflow-java/build.gradle b/runners/google-cloud-dataflow-java/build.gradle
index b814c70..eed8f19 100644
--- a/runners/google-cloud-dataflow-java/build.gradle
+++ b/runners/google-cloud-dataflow-java/build.gradle
@@ -45,7 +45,7 @@
   filter org.apache.tools.ant.filters.ReplaceTokens, tokens: [
     'dataflow.legacy_environment_major_version' : '8',
     'dataflow.fnapi_environment_major_version' : '8',
-    'dataflow.container_version' : 'beam-master-20210429',
+    'dataflow.container_version' : 'beam-master-20210503',
     'dataflow.container_base_repository' : 'gcr.io/cloud-dataflow/v1beta3',
   ]
 }