Fix duplicate OCR test declarations in tests

[etherlink-intern]

Motivation

• Duplicate Vision OCR test blocks and helper definitions in the test file caused Swift Testing macro redeclaration and conditional compilation mismatches, which broke swift test on CI.
• The conditional compilation branches needed to be consolidated so only one Vision-enabled path and one fallback path exist.

Description

• Removed the duplicated Vision-enabled test block in Tests/SwiftMarkItDownTests/SwiftMarkItDownTests.swift so the test is declared only once.
• Removed the duplicated OCR helper definitions (OCRSample, renderedOCRSamples, renderOCRImage) and left a single helper implementation behind a balanced #if ... #endif guard.
• Ensured conditional compilation blocks are balanced to avoid #else/#endif and macro redeclaration errors during test macro expansion.

Testing

• Ran swift test and all tests passed (10 tests executed and passed).
• Ran Scripts/smoke-test.sh and it completed successfully.

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Codex Task