Update CODEOWNERS

[chompomonim]

I think it is worth to extend code owners by people who're contributing into node for more that a half year. Also deleting contributors who're not a part of core team anymore.

[codecov-commenter]

Codecov Report

Merging #3414 (19b316a) into master (5d2a405) will decrease coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3414      +/-   ##
==========================================
- Coverage   43.69%   43.63%   -0.07%     
==========================================
  Files         311      311              
  Lines       13682    13682              
==========================================
- Hits         5979     5970       -9     
- Misses       6985     6990       +5     
- Partials      718      722       +4     

Impacted Files	Coverage Δ
core/policy/oracle.go	83.87% <0.00%> (-6.46%)	⬇️
requests/dialer_swarm.go	73.68% <0.00%> (-3.51%)	⬇️
nat/traversal/pinger.go	72.13% <0.00%> (-1.64%)	⬇️
p2p/channel.go	72.99% <0.00%> (+0.84%)	⬆️

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