Clarify that by default the gem_name is rails #313

Job	Run time
Rubocop	18s
Ruby 3.0 / Gemfile	18s
Ruby 3.1 / Gemfile	24s
Ruby 3.2 / Gemfile	22s
Ruby 3.3 / Gemfile	20s
Ruby 3.0 / gemfiles/activesupport_6.1.gemfile	16s
Ruby 3.1 / gemfiles/activesupport_6.1.gemfile	22s
Ruby 3.2 / gemfiles/activesupport_6.1.gemfile	22s
Ruby 3.3 / gemfiles/activesupport_6.1.gemfile	22s
Ruby 3.0 / gemfiles/activesupport_7.0.gemfile	12s
Ruby 3.1 / gemfiles/activesupport_7.0.gemfile	15s
Ruby 3.2 / gemfiles/activesupport_7.0.gemfile	15s
Ruby 3.3 / gemfiles/activesupport_7.0.gemfile	14s
Ruby 3.0 / gemfiles/activesupport_7.1.gemfile	19s
Ruby 3.1 / gemfiles/activesupport_7.1.gemfile	19s
Ruby 3.2 / gemfiles/activesupport_7.1.gemfile	21s
Ruby 3.3 / gemfiles/activesupport_7.1.gemfile	21s
Ruby 3.1 / gemfiles/activesupport_7.2.gemfile	18s
Ruby 3.2 / gemfiles/activesupport_7.2.gemfile	22s
Ruby 3.3 / gemfiles/activesupport_7.2.gemfile	18s
Ruby 3.1 / gemfiles/activesupport_edge.gemfile	28s
Ruby 3.2 / gemfiles/activesupport_edge.gemfile	26s
Ruby 3.3 / gemfiles/activesupport_edge.gemfile	26s
	7m 38s

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