Simplify the GitHub actions config using matrix #593

Job	Run time
Tests (Ruby 3.1, Rails 7.0, sprockets)	1m 0s
Tests (Ruby 3.1, Rails 7.1, sprockets)	42s
Tests (Ruby 3.1, Rails 7.0, propshaft)	59s
Tests (Ruby 3.1, Rails 6.1, sprockets)	1m 31s
Tests (Ruby 3.2, Rails 7.0, propshaft)	44s
Tests (Ruby 3.1, Rails 7.1, propshaft)	44s
Tests (Ruby 3.1, Rails 7.2, propshaft)	1m 2s
Tests (Ruby 3.2, Rails 7.0, sprockets)	43s
Tests (Ruby 3.2, Rails 7.1, sprockets)	46s
Tests (Ruby 3.2, Rails 6.1, sprockets)	1m 31s
Tests (Ruby 3.2, Rails 7.2, sprockets)	1m 10s
Tests (Ruby 3.3, Rails 7.0, propshaft)	49s
Tests (Ruby 3.2, Rails 7.1, propshaft)	40s
Tests (Ruby 3.1, Rails 7.2, sprockets)	58s
Tests (Ruby 3.3, Rails 7.0, sprockets)	46s
Tests (Ruby 3.3, Rails 7.1, propshaft)	49s
Tests (Ruby 3.3, Rails 6.1, sprockets)	1m 36s
Tests (Ruby 3.3, Rails 7.1, sprockets)	47s
Tests (Ruby 3.3, Rails main, propshaft)	1m 4s
Tests (Ruby 3.2, Rails main, propshaft)	1m 3s
Tests (Ruby 3.2, Rails 8.0, propshaft)	1m 9s
Tests (Ruby 3.4, Rails 7.0, propshaft)	1m 52s
Tests (Ruby 3.4, Rails 7.0, sprockets)	1m 59s
Tests (Ruby 3.3, Rails 7.2, propshaft)	1m 8s
Tests (Ruby 3.4, Rails 7.1, propshaft)	40s
Tests (Ruby 3.4, Rails 6.1, sprockets)	2m 4s
Tests (Ruby 3.4, Rails 7.1, sprockets)	40s
Tests (Ruby 3.4, Rails 7.2, propshaft)	57s
Tests (Ruby 3.3, Rails 7.2, sprockets)	1m 6s
Tests (Ruby 3.4, Rails main, propshaft)	1m 2s
Tests (Ruby 3.4, Rails 8.0, propshaft)	59s
Tests (Ruby 3.3, Rails 8.0, propshaft)	1m 8s
Tests (Ruby 3.4, Rails 7.2, sprockets)	1m 3s
Tests (Ruby 3.2, Rails 7.2, propshaft)	59s
	36m 10s

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