Hi Hanuma Suresh,
You can use below powershell to remove the delegation on a subnet , it's only required update with your values:
Connect-AzAccount
$vnet = Get-AzVirtualNetwork -ResourceGroupName "<your RG name>" -Name "<Vnet Name>"
$subnet = Get-AzVirtualNetworkSubnetConfig -Name "<Subnet Name>" -VirtualNetwork $vnet
$subnet = Remove-AzDelegation -Name "<your delegation example: Microsoft.DBforMySQL/flexibleServers>" -Subnet $subnet
Set-AzVirtualNetwork -VirtualNetwork $vnet
If the information helped address your question, please Accept the answer.
Luis