deps: Drop Ruby v2.6 / Require Ruby v2.7+ #236

Job	Run time
test (2.7, gemfiles/jekyll_3.9.gemfile)	22s
test (2.7, gemfiles/jekyll_4.0.gemfile)	22s
test (2.7, gemfiles/jekyll_4.1.gemfile)	25s
test (2.7, gemfiles/jekyll_4.2.gemfile)	21s
test (2.7, gemfiles/jekyll_4.3.gemfile)	21s
test (3.0, gemfiles/jekyll_3.9.gemfile)	9s
test (3.0, gemfiles/jekyll_4.0.gemfile)	8s
test (3.0, gemfiles/jekyll_4.1.gemfile)	12s
test (3.0, gemfiles/jekyll_4.2.gemfile)	12s
test (3.0, gemfiles/jekyll_4.3.gemfile)	7s
test (3.1, gemfiles/jekyll_3.9.gemfile)	13s
test (3.1, gemfiles/jekyll_4.0.gemfile)	10s
test (3.1, gemfiles/jekyll_4.1.gemfile)	11s
test (3.1, gemfiles/jekyll_4.2.gemfile)	14s
test (3.1, gemfiles/jekyll_4.3.gemfile)	8s
test (3.2, gemfiles/jekyll_3.9.gemfile)	8s
test (3.2, gemfiles/jekyll_4.0.gemfile)	8s
test (3.2, gemfiles/jekyll_4.1.gemfile)	12s
test (3.2, gemfiles/jekyll_4.2.gemfile)	8s
test (3.2, gemfiles/jekyll_4.3.gemfile)	12s
test (3.3, gemfiles/jekyll_3.9.gemfile)	8s
test (3.3, gemfiles/jekyll_4.0.gemfile)	9s
test (3.3, gemfiles/jekyll_4.1.gemfile)	8s
test (3.3, gemfiles/jekyll_4.2.gemfile)	9s
test (3.3, gemfiles/jekyll_4.3.gemfile)	8s
	5m 5s

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