As of today, Microsoft doesn’t give option to uninstall the Xbox Game Bar from the Apps & Features. But you can uninstall it with PowerShell.
First run the following script to see the list of Xbox:
dism /Online /Get-ProvisionedAppxPackages | Select-String PackageName | Select-String xbox
Then run the following:
Get-ProvisionedAppxPackage -Online | `
Where-Object { $_.PackageName -match "xbox" } | `
ForEach-Object { Remove-ProvisionedAppxPackage -Online -PackageName $_.PackageName }