Remove ruby23 support

[ghost]

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[codecov]

Codecov Report

Merging #1440 (b0bed4f) into cosmos4 (c3ec0d2) will increase coverage by 0.03%.
The diff coverage is 100.00%.

❗ Current head b0bed4f differs from pull request most recent head 574be04. Consider uploading reports for the commit 574be04 to get more accurate results

@@             Coverage Diff             @@
##           cosmos4    #1440      +/-   ##
===========================================
+ Coverage    78.66%   78.69%   +0.03%     
===========================================
  Files          165      165              
  Lines        15722    15707      -15     
===========================================
- Hits         12367    12361       -6     
+ Misses        3355     3346       -9     

Impacted Files	Coverage Δ
lib/cosmos/io/json_drb.rb	100.00% <ø> (+2.59%)	⬆️
lib/cosmos/packets/packet_item_limits.rb	100.00% <100.00%> (+3.38%)	⬆️
lib/cosmos/packets/structure_item.rb	77.56% <100.00%> (+1.02%)	⬆️
lib/cosmos/system/system.rb	88.42% <100.00%> (ø)

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