Remove retired Go Report Card badge from README

[EchterTimo]

Description

• Removed retired Go Report Card badge

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (please discuss with the team first; Syft is 1.0 software and we won't accept breaking changes without going to 2.0)
• Documentation (updates the documentation)
• Chore (improve the developer experience, fix a test flake, etc, without changing the visible behavior of Syft)
• Performance (make Syft run faster or use less memory, without changing visible behavior much)

Checklist

• I have added unit tests that cover changed behavior
• I have tested my code in common scenarios and confirmed there are no regressions
• I have added comments to my code, particularly in hard-to-understand sections

Issue references

[Copilot]

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