Narrow YieldExplainers action prop type to match actual usage

[coderabbitai]

The YieldExplainers component's type signature includes action: 'enter' | 'exit' | 'claim', but in practice it only receives 'enter' or 'exit' because YieldForm guards against the claim action with {!isClaimAction && <YieldExplainers ... />}.

The type signature should be narrowed to action: 'enter' | 'exit' to accurately reflect actual usage and prevent confusion.

File: src/pages/Yields/components/YieldExplainers.tsx

Context:

• Originated from PR fix: yield withdraw polishes #11784: fix: yield withdraw polishes #11784
• Comment: fix: yield withdraw polishes #11784 (comment)
• Requested by @gomesalexandre

[gomesalexandre]

closed by #12073