fix(logrusx): prettify on json_pretty only

[aeneasr]

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• I have read the contributing guidelines
• I have read the security policy
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
  confirm that I got green light (please contact
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• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation within the code base (if appropriate)

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