Remove support for Rails 6.0 and Ruby 2.7 #55

Job	Run time
build (3.0, Gemfile.rails-6.1.x, mysql)	2m 4s
build (3.0, Gemfile.rails-6.1.x, postgres)	1m 48s
build (3.0, Gemfile.rails-6.1.x, sqlite)	1m 32s
build (3.0, Gemfile.rails-7.0.x, mysql)	1m 39s
build (3.0, Gemfile.rails-7.0.x, postgres)	2m 0s
build (3.0, Gemfile.rails-7.0.x, sqlite)	1m 26s
build (3.1, Gemfile.rails-6.1.x, mysql)	1m 51s
build (3.1, Gemfile.rails-6.1.x, postgres)	1m 51s
build (3.1, Gemfile.rails-6.1.x, sqlite)	1m 52s
build (3.1, Gemfile.rails-7.0.x, mysql)	1m 47s
build (3.1, Gemfile.rails-7.0.x, postgres)	1m 47s
build (3.1, Gemfile.rails-7.0.x, sqlite)	2m 5s
build (3.2, Gemfile.rails-6.1.x, mysql)	2m 12s
build (3.2, Gemfile.rails-6.1.x, postgres)	1m 54s
build (3.2, Gemfile.rails-6.1.x, sqlite)	1m 36s
build (3.2, Gemfile.rails-7.0.x, mysql)	1m 52s
build (3.2, Gemfile.rails-7.0.x, postgres)	1m 50s
build (3.2, Gemfile.rails-7.0.x, sqlite)	1m 31s
	32m 37s

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