🐛 fix: add Content-Type header to gateway request

[Aloxaf]

💻 变更类型 | Change Type

• [ ] ✨ feat
• [x] 🐛 fix
• [ ] ♻️ refactor
• [ ] 💄 style
• [ ] 🔨 chore
• [ ] 📝 docs

🔀 变更说明 | Description of Change

📝 补充信息 | Additional Information

[lobehubbot]

👍 @Aloxaf
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