flags: remove peerdb flag

[xenowits]

Remove --p2p-peerdb flag, so peerDB now defaults to a new in-memory database.

category: refactor
ticket: #644

[codecov]

Codecov Report

Merging #657 (5b1ee59) into main (40209f9) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #657      +/-   ##
==========================================
+ Coverage   55.00%   55.02%   +0.02%     
==========================================
  Files          98       98              
  Lines        9510     9510              
==========================================
+ Hits         5231     5233       +2     
+ Misses       3528     3527       -1     
+ Partials      751      750       -1     

Impacted Files	Coverage Δ
cmd/run.go	100.00% <ø> (ø)
p2p/config.go	62.50% <ø> (ø)
p2p/discovery.go	50.00% <100.00%> (+0.74%)	⬆️
core/qbft/qbft.go	81.89% <0.00%> (+0.43%)	⬆️

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