fix(crypto): multisig legacy allow signatures property

[air1one]

Summary

Resolves #3444 by allowing in json schema validation legacy multisig to have the "signatures" property (which is handled fine by core then).

Checklist

• Documentation (if necessary)
• Tests (if necessary)
• Ready to be merged

[air1one]

ok so now v2 multisig registration txs are not accepted 😄 working on it

[codecov]

Codecov Report

Merging #3489 into 2.6 will increase coverage by <.01%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##              2.6    #3489      +/-   ##
==========================================
+ Coverage   66.17%   66.18%   +<.01%     
==========================================
  Files         439      439              
  Lines       12466    12466              
  Branches     1710     1710              
==========================================
+ Hits         8249     8250       +1     
+ Misses       4183     4182       -1     
  Partials       34       34

Impacted Files	Coverage Δ
packages/crypto/src/transactions/registry.ts	71.05% <ø> (ø)	⬆️
packages/core-api/src/handlers/peers/controller.ts	85.1% <83.33%> (ø)	⬆️
packages/core-transaction-pool/src/storage.ts	100% <0%> (+2.5%)	⬆️

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