Still running CI for end-of-life Rubies (2.6, 2.7)

[larouxn]

Can probably drop support for (or at least remove from CI) at least Ruby 2.6, maybe Ruby 2.7 as well, as they're both end-of-life. Just seeing now, Ruby 3.0 is going to be end-of-life by end of March next year.

payment_icons/.github/workflows/ruby-ci.yml

Lines 20 to 24 in 9c8f138

	- 2.6
	- 2.7
	- 3.0
	- 3.1
	- 3.2

Ruby 3.0
status: security maintenance
release date: 2020-12-25
normal maintenance until: 2023-04-01
EOL: 2024-03-31 (expected)

Ruby 2.7
status: eol
release date: 2019-12-25
normal maintenance until: 2022-04-01
EOL: 2023-03-31

Ruby 2.6
status: eol
release date: 2018-12-25
normal maintenance until: 2021-04-01
EOL: 2022-04-12

https://www.ruby-lang.org/en/downloads/branches/