Fix incorrect license detection in dragon4.c

[Kaushik-Kumar-CEG]

Fixes #4584

Description

This PR fixes an incorrect license detection in NumPy's dragon4.c, where the text "As a special exception" was incorrectly triggering a generic-exception match.

Changes:

• Modified license-intro_8.RULE: Downgraded this rule from is_license_intro to is_license_clue. This ensures the phrase contributes to evidence but does not trigger a false positive when found alone.
• Added false-positive_dragon4.RULE: Added a specific false positive rule to ignore the misleading text ("As a special exception the smallest normal value") found in dragon4.c.

Verification:

• Reproduced the issue locally: confirmed generic-exception was originally detected.
• Verified the fix: confirmed the detection is gone after the changes.
• Validated the rule downgrade: confirmed that license-intro_8.RULE correctly behaves as a clue (no detection) when isolated.

Tasks

• Reviewed contribution guidelines
• PR is descriptively titled 📄 and links the original issue above 🔗
• Tests pass -- look for a green checkbox ✔️ a few minutes after opening your PR (Verified fix locally)
• Commits are in uniquely-named feature branch and has no merge conflicts 📂
• Updated documentation pages (if applicable)
• Updated CHANGELOG.rst (if applicable)

[Kaushik-Kumar-CEG]

@pombredanne @AyanSinhaMahapatra

This PR resolves the false positive generic-exception detection in dragon4.c. Verified the fix, it works locally.

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