Remove support for Rails 6.0 and Ruby 2.7 #54

Job	Run time
build (3.0, Gemfile.rails-6.1.x, mysql)	2m 1s
build (3.0, Gemfile.rails-6.1.x, postgres)	2m 18s
build (3.0, Gemfile.rails-6.1.x, sqlite)	1m 42s
build (3.0, Gemfile.rails-7.0.x, mysql)	2m 22s
build (3.0, Gemfile.rails-7.0.x, postgres)	2m 1s
build (3.0, Gemfile.rails-7.0.x, sqlite)	1m 50s
build (3.1, Gemfile.rails-6.1.x, mysql)	2m 9s
build (3.1, Gemfile.rails-6.1.x, postgres)	2m 42s
build (3.1, Gemfile.rails-6.1.x, sqlite)	2m 11s
build (3.1, Gemfile.rails-7.0.x, mysql)	2m 36s
build (3.1, Gemfile.rails-7.0.x, postgres)	2m 26s
build (3.1, Gemfile.rails-7.0.x, sqlite)	1m 58s
build (3.2, Gemfile.rails-6.1.x, mysql)	2m 1s
build (3.2, Gemfile.rails-6.1.x, postgres)	2m 3s
build (3.2, Gemfile.rails-6.1.x, sqlite)	1m 50s
build (3.2, Gemfile.rails-7.0.x, mysql)	2m 44s
build (3.2, Gemfile.rails-7.0.x, postgres)	2m 0s
build (3.2, Gemfile.rails-7.0.x, sqlite)	1m 51s
	38m 45s

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