fix error message of too short NEW_SYSTEM_SECRET

[sawadashota]

Related issue

none

Proposed changes

Show count of NEW_SYSTEM_SECRET length when NEW_SYSTEM_SECRET is too short

Checklist

• I have read the contributing guidelines
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  vulnerability, I confirm that I got green light (please contact hi@ory.sh) from the maintainers to push the changes.
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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)
• I have documented my changes in the developer guide (if appropriate)

Further comments

none

[aeneasr]

thanks!