fix: Fix verification of proofs for specs with more than 2 children per node (in Rust implementation)

[mappum]

This PR fixes the Rust right_branches_are_empty implementation, specifically for specs which have more than 2 children per node (e.g. Merk).

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 66.01%. Comparing base (3645479) to head (2bc72db).

Files	Patch %	Lines
rust/src/verify.rs	50.00%	1 Missing :warning:

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #290       +/-   ##
===========================================
+ Coverage   51.39%   66.01%   +14.62%     
===========================================
  Files          23        7       -16     
  Lines        9341     3652     -5689     
  Branches       86        0       -86     
===========================================
- Hits         4801     2411     -2390     
+ Misses       4175     1241     -2934     
+ Partials      365        0      -365     

Flag	Coverage Δ
go	?
rust	66.01% <50.00%> (ø)
typescript	?

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