Drop old ruby support and fix coverage publishing

[andrcuns]

• Drop support for EOL ruby versions 2.7 and 3.0
• Update coverage action

[github-actions[bot]]

Code Coverage Summary

Filename                                       Stmts    Miss  Cover    Missing
-------------------------------------------  -------  ------  -------  ------------------------------
lib/sidekiq_alive.rb                              89       5  94.00%   27, 74, 80-81, 95
lib/sidekiq_alive/config.rb                       22       0  100.00%
lib/sidekiq_alive/helpers.rb                      26       4  85.00%   11, 27, 34, 37
lib/sidekiq_alive/redis.rb                         8       0  100.00%
lib/sidekiq_alive/redis/base.rb                   17       6  65.00%   7, 11, 15, 19, 23, 27
lib/sidekiq_alive/redis/redis_client_gem.rb       24       1  96.00%   41
lib/sidekiq_alive/redis/redis_gem.rb              21       8  62.00%   11, 15, 19, 23, 27, 31, 35, 41
lib/sidekiq_alive/server.rb                       15       1  93.00%   23
lib/sidekiq_alive/server/base.rb                  27       6  78.00%   11-12, 19-23
lib/sidekiq_alive/server/default.rb               48       4  92.00%   60-63
lib/sidekiq_alive/server/http_server.rb           65       7  89.00%   24-27, 80-81, 107, 136
lib/sidekiq_alive/server/rack.rb                  38       2  95.00%   47-48
lib/sidekiq_alive/worker.rb                       17       1  94.00%   28
spec/redis_spec.rb                                12       0  100.00%
spec/server/default_spec.rb                       39       0  100.00%
spec/server/rack_spec.rb                          40       0  100.00%
spec/server_spec.rb                               76       6  92.00%   69-72, 125-128
spec/sidekiq_alive_spec.rb                       106       4  96.00%   106-109, 141
spec/worker_spec.rb                               32       0  100.00%
TOTAL                                            722      55  92.00%

Results for commit: e90fdae2a0b1e72cbf5690d43ba1f961cd9d5091

Minimum allowed coverage is 90%

:recycle: This comment has been updated with latest results

[andrcuns]

@arturictus Could you please review, this should unblock automated dependency update PR's

[arturictus]

Thanks @andrcuns