small fix for multikey local testnet

[sstanculeanu]

Reasoning behind the pull request

• the observers that hold the keys should be one in each shard for local testnets

Proposed changes

Testing procedure

Pre-requisites

Based on the Contributing Guidelines the PR author and the reviewers must check the following requirements are met:

• was the PR targeted to the correct branch?
• if this is a larger feature that probably needs more than one PR, is there a feat branch created?
• if this is a feat branch merging, do all satellite projects have a proper tag inside go.mod?

[github-actions]

📊 MultiversX Automated Test Report: View Report

🔄 Build Details:

• mx-chain-go Commit Hash: 6426c1c3087e5a0120ade855c3f84f5950abd13d
• Current Branch: fix_local_testnet_multikey
• mx-chain-go Target Branch: rc/andromeda
• mx-chain-simulator-go Target Branch: rc/andromeda
• mx-chain-testing-suite Target Branch: rc/andromeda

🚀 Environment Variables:

• TIMESTAMP: 24032025-164806
• PYTEST_EXIT_CODE: 1
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