undo resource size increase for chrome build

.circleci/config.yml

@@ -62,7 +62,7 @@ jobs:
       # Specify service dependencies here if necessary
       # CircleCI maintains a library of pre-built images
       # documented at https://circleci.com/docs/2.0/circleci-images/
-    resource_class: 2xlarge
+    resource_class: xlarge
       # - image: circleci/mongo:3.4.4
     environment:
       - COMMIT_AUTHOR_EMAIL: "yann@ethereum.org"
@@ -95,7 +95,7 @@ jobs:
       # Specify service dependencies here if necessary
       # CircleCI maintains a library of pre-built images
       # documented at https://circleci.com/docs/2.0/circleci-images/
-    resource_class: 2xlarge
+    resource_class: xlarge
       # - image: circleci/mongo:3.4.4
     environment:
       - COMMIT_AUTHOR_EMAIL: "yann@ethereum.org"