fix(incentive): filter zero rewards from query

[kerber0x]

Description and Motivation

This PR improves the incentive rewards query by filtering the zero amount rewards. Instead, it returns an empty vector.

Related Issues

#212

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Checklist:

• I have read Migaloo's contribution guidelines.
• My pull request has a sound title and description (not something vague like Update index.md)
• All existing and new tests are passing.
• I updated/added relevant documentation.
• The code is formatted properly cargo fmt --all --.
• Clippy doesn't report any issues cargo clippy -- -D warnings.
• I have regenerated the schemas if needed cargo schema.

[codecov]

Codecov Report

Patch coverage: 99.52% and project coverage change: +0.04 🎉

Comparison is base (c6ee3e1) 94.56% compared to head (6bfe9b3) 94.60%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #214      +/-   ##
==========================================
+ Coverage   94.56%   94.60%   +0.04%     
==========================================
  Files         208      208              
  Lines       22937    23138     +201     
==========================================
+ Hits        21690    21890     +200     
- Misses       1247     1248       +1     

Impacted Files	Coverage Δ
...-network/vault_factory/src/execute/create_vault.rs	100.00% <ø> (ø)
...ub/pool-network/incentive/src/tests/integration.rs	97.80% <99.52%> (+0.14%)	⬆️
.../pool-network/incentive/src/queries/get_rewards.rs	98.41% <100.00%> (+0.02%)	⬆️

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[0xFable]

LGTM, small sensible change.