fix: duplicate keyword 'constants' in Solidity syntax highlighting

[kilavvy]

This PR fixes a duplicate keyword in the Solidity syntax highlighting configuration. The word 'constants' was incorrectly included when 'constant' is already present in the keywords list.

Changes made:

• Removed duplicate keyword 'constants' from the keywords array
• Kept the correct form 'constant' which is the proper Solidity keyword

This change helps maintain cleaner and more accurate syntax highlighting for Solidity files in the Remix editor.

[netlify]

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