This is a follow-up to 3121412
/cc @rafaelfranca
This will remove deprecation warnings from the PostgreSQL suite:
```
DEPRECATION WARNING: #capture(stream) is deprecated and will be removed in the next release. (called from capture at /Users/senny/Projects/rails/activesupport/lib/active_support/core_ext/kernel/reporting.rb:89)
/Users/senny/Projects/rails/activesupport/lib/active_support/core_ext/kernel/reporting.rb:89:in `capture'
/Users/senny/Projects/rails/activerecord/test/cases/adapters/postgresql/composite_test.rb:73:in `ensure_warning_is_issued'
/Users/senny/Projects/rails/activerecord/test/cases/adapters/postgresql/composite_test.rb:48:in `test_column'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest/test.rb:106:in `block (3 levels) in run'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest/test.rb:204:in `capture_exceptions'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest/test.rb:103:in `block (2 levels) in run'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest/test.rb:256:in `time_it'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest/test.rb:102:in `block in run'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest.rb:317:in `on_signal'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest/test.rb:276:in `with_info_handler'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest/test.rb:101:in `run'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest.rb:759:in `run_one_method'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest.rb:293:in `run_one_method'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest.rb:287:in `block (2 levels) in run'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest.rb:286:in `each'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest.rb:286:in `block in run'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest.rb:317:in `on_signal'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest.rb:306:in `with_info_handler'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest.rb:285:in `run'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest.rb:149:in `block in __run'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest.rb:149:in `map'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest.rb:149:in `__run'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest.rb:126:in `run'
/Users/senny/Projects/rails/.bundle/gems/minitest-5.3.3/lib/minitest.rb:55:in `block in autorun'
```