test: try ruby 2.7.2 / node 14 with mastodon

.circleci/config.yml

@@ -9,9 +9,7 @@ jobs:
   build_and_test:
     working_directory: ~/pinafore
     docker:
-        # see https://discuss.circleci.com/t/build-failed-the-engine-node-is-incompatible-with-this-module-expected-version-12-x-got-14-15-0/37921/7
-        # we want Node v12, not v14
-      - image: circleci/ruby@sha256:b018ec2a8f0bbf06880735d2801402bad316c465edb60663be83ac8f1086b805
+      - image: circleci/ruby:2.7.2-node-browsers
       - image: circleci/postgres:12.2
         environment:
           POSTGRES_USER: pinafore

bin/mastodon-config.js

@@ -17,9 +17,7 @@ DB_NAME=${DB_NAME}
 DB_PASS=${DB_PASS}
 `
 
-// Need a Ruby version that CircleCI bundles with Node v12, not Node v14 which doesn't
-// work for streaming
-export const RUBY_VERSION = '2.6.6'
+export const RUBY_VERSION = '2.7.2'
 
 export const mastodonDir = path.join(__dirname, '../mastodon')