config: set Aspidochelone hard fork for mainnet

[roman-khimov]

See neo-project/neo-node#862. It's not yet official, but this change makes
testing against mainnet dumps easier for now.

[codecov]

Codecov Report

Merging #2520 (c605cfb) into master (8055952) will decrease coverage by 0.07%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2520      +/-   ##
==========================================
- Coverage   85.10%   85.02%   -0.08%     
==========================================
  Files         294      294              
  Lines       37005    37005              
==========================================
- Hits        31494    31465      -29     
- Misses       4187     4219      +32     
+ Partials     1324     1321       -3     

Impacted Files	Coverage Δ
pkg/services/oracle/oracle.go	72.86% <0.00%> (-15.51%)	⬇️
pkg/services/oracle/request.go	57.99% <0.00%> (-5.03%)	⬇️
pkg/consensus/consensus.go	73.43% <0.00%> (+0.44%)	⬆️

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