refactor(scanner/redhatbase): strictly parse updatable package line

[MaineK00n]

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What did you implement:

Fixes #2217

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

$ vuls scan
...
Scan Summary
================
docker	amazon2023.7.20250512	165 installed, 4 updatable





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To send a report, run vuls report -h.

Checklist:

You don't have to satisfy all of the following.

• Write tests
• Write documentation
• Check that there aren't other open pull requests for the same issue/feature
• Format your source code by make fmt
• Pass the test by make test
• Provide verification config / commands
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES

Reference

[shino]

🎊