[KIP-149] Relax system contract condition

[hyeonLewis]

Proposed changes

This PR suggests to relax the condition of system contract. The immutable smart contract can be system contract.

Types of changes

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• Bugfix
• KIP Proposal
• KIP Improvement

Checklist

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• Used the suggested template: https://github.com/kaiachain/KIPs/blob/main/kip-template.md
• I have read the CLA and signed by comment I have read the CLA Document and I hereby sign the CLA in first time contribution
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

Related issues

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Further comments

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