Fix pg: symbol lookup error, pg_ext.so: undefined symbol: rb_tainted_…

…str_new2

See: https://status.heroku.com/incidents/1940

Engineers found that Ruby Private Space apps with pg gem 1.2.0 or above are affected. We would like to ask our customers to downgrade pg gem to 1.1.4 with editing the corresponding line in the Gemfile like

'pg', '~> 1.1.4'

gemfiles/6.0.gemfile

@@ -4,7 +4,7 @@ gem 'activerecord', '~> 6.0.0'
 
 group :test do
   gem 'mysql2', '0.5.1' if %w[mysql makara_mysql].include?(ENV['DB'])
-  gem 'pg', '~> 0.18' if %w[pg makara_pg].include?(ENV['DB'])
+  gem 'pg', '~> 1.1.4' if %w[pg makara_pg].include?(ENV['DB'])
   gem 'makara', '~> 0.4.1' if %w[makara_mysql makara_pg].include?(ENV['DB'])
   gem 'simplecov', '< 0.18'
   gem 'pluck_all', '>= 2.0.4'