Refactor randomPeer function to use local variable

[AnkushinDaniil]

The randomPeer function in syncService has been refactored to use a local variable store instead of accessing s.host.Peerstore() multiple times. This reduces unnecessary function calls.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 78.34%. Comparing base (1ff5e2c) to head (511618e). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2158 +/- ## ========================================== - Coverage 78.38% 78.34% -0.05% ========================================== Files 100 100 Lines 9220 9220 ========================================== - Hits 7227 7223 -4 - Misses 1354 1355 +1 - Partials 639 642 +3 ```

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