refactor: no plain-text private key in configuration file

[yangby-cryptape]

What this PR does / why we need it?

Resolve the issue which was originally in #1471 (comment).

The files devtools/chain/k8s/sync_nodes/node_[567].toml were broken since #1471.
After confirming with @KaoImin, these files will be removed in this PR.

What is the impact of this PR?

No Breaking Change

CI Settings

CI Usage

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CI Switch

• Web3 Compatible Tests
• OCT 1-5 And 12-15
• OCT 6-10
• OCT 11
• OCT 16-19
• v3 Core Tests

CI Description

CI Name	Description
Web3 Compatible Test	Test the Web3 compatibility of Axon
v3 Core Test	Run the compatibility tests provided by Uniswap V3
OCT 1-5 | 6-10 | 11 | 12-15 | 16-19	Run the compatibility tests provided by OpenZeppelin

[github-actions]

CI tests run on commit:

• commit id: a99294f

CI test list:

• OCT 1-5 And 12-15
• OCT 6-10
• OCT 11
• OCT 16-19
• v3 Core Tests
• Web3 Compatible Tests

Please check ci test results later.