Issue #3194401: Switch to CircleCI as the default automated testing platform

.circleci/config.yml

@@ -48,7 +48,7 @@ jobs:
             sudo -E docker-php-ext-configure pdo_mysql --with-pdo-mysql=mysqlnd
             sudo -E docker-php-ext-install bcmath pdo_mysql
             sudo -E docker-php-ext-install gd
-            sudo -E docker-php-ext-install mbstring xml cgi cli common curl imap intl pspell sqlite3 tidy opcache json bz2 readline xmlrpc enchant xsl
+            sudo -E docker-php-ext-install mbstring xml cgi cli common curl imap intl pspell sqlite3 tidy json xmlrpc xsl
             sudo service apache2 restart
 
       ## Change PHP Configurations.