fix: Meta data type error fixed.

[kidunot89]

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What does this implement/fix? Explain your changes.

• Returns flatten array meta values bypassing the array to string conversion array.
• As shop-level cap check to coupon query.

Does this close any currently open issues?

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Any other comments?

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Where has this been tested?

• WooGraphQL Version: …
• WPGraphQL Version: …
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