fix: Clarify emphasis test guidance to reduce false positives

[v-sohmondal]

Summary

fixes: #7650
Updates the Semantics > Emphasis assessment to clarify that bold/italic text used purely for visual design (labels, visual separation, hierarchy) does NOT require <strong> or <em> elements—only text conveying semantic emphasis does.

Changes

src/assessments/semantics/test-steps/emphasis.tsx

• Updated "How to Test" instructions to focus on semantic emphasis, not just visual styling

src/content/test/semantics/emphasis.tsx

• Added guidance clarifying when semantic markup is NOT needed
• Added new Pass/Fail examples for SKU heading and breadcrumb separator scenarios

Solution

Updated the test instructions and guidance content to:

1. Clarify the distinction between semantic emphasis and visual styling
2. Provide clear guidance that bold/italic used purely for design purposes does NOT require semantic markup
3. Add new Pass/Fail examples demonstrating:
   • SKU Heading: Using <strong> inside a heading for visual styling is unnecessary since the heading already provides semantic importance
   • Breadcrumb Separator: Using <em> for italic separators is incorrect since they're for visual presentation, not emphasis

[v-jitendjain]

/azp run

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