Bump puma from 5.6.8 to 5.6.9 #6157

Job	Run time
Tests (mysql, rails test test/unit)	24m 46s
Tests (mysql, rails test test/functional)	33m 13s
Tests (mysql, rails test test/integration)	21m 23s
Tests (mysql, rspec spec)	3m 39s
Tests (mysql, rake assets:precompile)	3m 31s
Tests (mysql, rake db:setup)	3m 42s
Tests (mysql, rake db:migrate)	3m 17s
Tests (mysql, rake seek:upgrade)	3m 57s
Tests (postgres, rails test test/unit)	24m 16s
Tests (sqlite3, rails test test/unit)	19m 25s
	2h 21m 9s

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