fix(amazon): check only major version of AL to find advisories

[DmitriyLewen]

Description

system-release can contain minor and patch version(e.g. 2023.3.20240304).
But we need to check only major version to get list of advisories for found OS.

Related issues

• Close bug(amazonlinux): Trivy marks Amazon Linux version as EOL if */system-release file uses 2023.xxx.xxx format #6294
• Amazon Linux 2023 flagged as EOL trivy-db#390

Checklist

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• I've added tests that prove my fix is effective or that my feature works.
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