Fix outdated gem count in README. #52

Job	Run time
test (2.5, test/gemfiles/rails_5_0.gemfile)	2m 58s
test (2.5, test/gemfiles/rails_5_1.gemfile)	2m 51s
test (2.5, test/gemfiles/rails_5_2.gemfile)	2m 49s
test (2.5, test/gemfiles/rails_6_0.gemfile)	2m 51s
test (2.5, test/gemfiles/rails_6_1.gemfile)	2m 47s
test (2.6, test/gemfiles/rails_5_0.gemfile)	2m 57s
test (2.6, test/gemfiles/rails_5_1.gemfile)	2m 43s
test (2.6, test/gemfiles/rails_5_2.gemfile)	2m 56s
test (2.6, test/gemfiles/rails_6_0.gemfile)	2m 56s
test (2.6, test/gemfiles/rails_6_1.gemfile)	3m 8s
test (2.7, test/gemfiles/rails_5_0.gemfile)	2m 54s
test (2.7, test/gemfiles/rails_5_1.gemfile)	3m 21s
test (2.7, test/gemfiles/rails_5_2.gemfile)	2m 42s
test (2.7, test/gemfiles/rails_6_0.gemfile)	2m 53s
test (2.7, test/gemfiles/rails_6_1.gemfile)	2m 51s
test (2.7, test/gemfiles/rails_7_0_sassc.gemfile)	3m 8s
test (2.7, test/gemfiles/rails_7_0_dartsass.gemfile)	59s
test (3.0, test/gemfiles/rails_6_0.gemfile)	1m 41s
test (3.0, test/gemfiles/rails_6_1.gemfile)	1m 33s
test (3.0, test/gemfiles/rails_7_0_sassc.gemfile)	1m 28s
test (3.0, test/gemfiles/rails_7_0_dartsass.gemfile)	23s
test (3.1, test/gemfiles/rails_6_1.gemfile)	1m 53s
test (3.1, test/gemfiles/rails_7_0_sassc.gemfile)	1m 32s
test (3.1, test/gemfiles/rails_7_0_dartsass.gemfile)	32s
test (2.5, test/gemfiles/rails_4_2.gemfile)	2m 51s
test (2.6, test/gemfiles/rails_4_2.gemfile)	2m 51s
	1h 2m 28s

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