Add missing brace in Gatt_Server_Example_Walkthrough.md (IDFGH-11590)

[Harrisonust]

No description provided.

[CLAassistant]

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[github-actions]

	Warnings
⚠️	The PR description looks very brief, please check if more details can be added.

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[esp-zhp]

Thank you for your report. In the future, we will optimize the documents.

[esp-zhp]

fixed f812863

[Alvin1Zhang]

Thanks for contribution again.