Discrepancy in supported Rubies

[leoarnold]

The GemSpec claims that the gem supports Ruby 2.6+

ruby-rrule/rrule.gemspec

Line 24 in 648bece

s.required_ruby_version = '>= 2.6.0'

but QA only checks against Ruby 3.0+

ruby-rrule/.github/workflows/test.yml

Lines 12 to 16 in 648bece

	ruby:
	- 3.0.0
	- 3.1.0
	- 3.2.0
	- 3.3.0

At time of writing this issue, Ruby 3.0 is EOL and Ruby 3.1+ are still maintained: https://endoflife.date/ruby

@rmitchell-sq Which shall it be: Restrict gem or extend CI?