Revert "[BEAM-8706] Bump antlr4 to 4.9.2"

This reverts commit f3fab5c1
diff --git a/buildSrc/src/main/groovy/org/apache/beam/gradle/BeamModulePlugin.groovy b/buildSrc/src/main/groovy/org/apache/beam/gradle/BeamModulePlugin.groovy
index f6d61b5..d2e2898 100644
--- a/buildSrc/src/main/groovy/org/apache/beam/gradle/BeamModulePlugin.groovy
+++ b/buildSrc/src/main/groovy/org/apache/beam/gradle/BeamModulePlugin.groovy
@@ -417,7 +417,6 @@
     // a dependency version which should match across multiple
     // Maven artifacts.
     def activemq_version = "5.14.5"
-    def antlr_version = "4.9.2"
     def autovalue_version = "1.8.1"
     def aws_java_sdk_version = "1.11.974"
     def aws_java_sdk2_version = "2.15.31"
@@ -467,8 +466,8 @@
         activemq_junit                              : "org.apache.activemq.tooling:activemq-junit:$activemq_version",
         activemq_kahadb_store                       : "org.apache.activemq:activemq-kahadb-store:$activemq_version",
         activemq_mqtt                               : "org.apache.activemq:activemq-mqtt:$activemq_version",
-        antlr                                       : "org.antlr:antlr4:$antlr_version",
-        antlr_runtime                               : "org.antlr:antlr4-runtime:$antlr_version",
+        antlr                                       : "org.antlr:antlr4:4.7",
+        antlr_runtime                               : "org.antlr:antlr4-runtime:4.7",
         args4j                                      : "args4j:args4j:2.33",
         auto_value_annotations                      : "com.google.auto.value:auto-value-annotations:$autovalue_version",
         avro                                        : "org.apache.avro:avro:1.8.2",