[tests-only] add coverage for idempotent tag removal

[nabim777]

Description

This PR adds tests for PR #12001.

The tests cover:

• Tag removal.
• Removing an already deleted tag.
• Searching files after tag removal.

Related Issue

• part of [QA] Add new automated tests #12472
• bug coverage for fixed PR fix(graph): make tag unassignment idempotent #12001

Motivation and Context

How Has This Been Tested?

• test environment:
• test case 1:
• test case 2:
• ...

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests only (no source changes)

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised:

[kw-security]

✅ Snyk checks have passed. No issues have been found so far.

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✅	Licenses	0	0	0	0	0 issues
✅	Code Security	0	0	0	0	0 issues

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