fix: Fixing leftover references to sha256 method

[traut]

Pull Request

Issue link(s):

• fix: Cleaning up the hashable content for the rule #4621

Summary - What I changed

Fixing the leftovers from #4621 - refactoring the usage of outdated sha256() method

How To Test

Checklist

• Added a label for the type of pr: bug, enhancement, schema, maintenance, Rule: New, Rule: Deprecation, Rule: Tuning, Hunt: New, or Hunt: Tuning so guidelines can be generated
• Added the meta:rapid-merge label if planning to merge within 24 hours
• Secret and sensitive material has been managed correctly
• Automated testing was updated or added to match the most common scenarios
• Documentation and comments were added for features that require explanation

Contributor checklist

• Have you signed the contributor license agreement?
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[eric-forte-elastic]

🟢 Manual review, looks good to me! 👍

[github-actions]

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Testing

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[eric-forte-elastic]

Appears that all have now been converted back from https://github.com/elastic/detection-rules/pull/4654/files#diff-2cdf98bba030d2fe3b81b454b0bc49f9e4d2558fa086d64e6e0b0e63780aa444L88