web-component-tester: Install babel runtime dependency

Bug: Issue 14172
Change-Id: Ib02c581523ada92e89311475eb44567df21c90a9
diff --git a/jenkins-docker/slave-node-wct/Dockerfile b/jenkins-docker/slave-node-wct/Dockerfile
index 4f755d8..b5274f9 100644
--- a/jenkins-docker/slave-node-wct/Dockerfile
+++ b/jenkins-docker/slave-node-wct/Dockerfile
@@ -18,5 +18,6 @@
       eslint-plugin-promise@"=4.0.1" \
       typescript \
       fried-twinkie@"^0.2.2" \
-      polylint polymer-cli
+      polylint polymer-cli \
+      @babel/runtime@"^7.13.9"
 RUN npm install --unsafe-perm -g 'web-component-tester@$WCT_VER'