Azure appservice using terraform gives error ""/providers/Microsoft.Web/sourceControls/GitHub" already exists"

I tried the below terraform code to create app Service with source control from this document.

My main.tf code referred from the document above but modified to print source_control resource id:-

# Configure the Azure provider
terraform {
  required_providers {
    azurerm = {
      source  = "hashicorp/azurerm"
      version = "~> 3.0.0"
    }
  }
  required_version = ">= 0.14.9"
}
provider "azurerm" {
  features {}
}

# Generate a random integer to create a globally unique name
resource "random_integer" "ri" {
  min = 10000
  max = 99999
}

# Create the resource group
resource "azurerm_resource_group" "rg" {
  name     = "myResourceGroup-${random_integer.ri.result}"
  location = "eastus"
}

# Create the Linux App Service Plan
resource "azurerm_service_plan" "appserviceplan" {
  name                = "webapp-asp-${random_integer.ri.result}"
  location            = azurerm_resource_group.rg.location
  resource_group_name = azurerm_resource_group.rg.name
  os_type             = "Linux"
  sku_name            = "B1"
}


resource "azurerm_linux_web_app" "webapp" {
  name                  = "webapp-${random_integer.ri.result}"
  location              = azurerm_resource_group.rg.location
  resource_group_name   = azurerm_resource_group.rg.name
  service_plan_id       = azurerm_service_plan.appserviceplan.id
  https_only            = true
  site_config { 
    minimum_tls_version = "1.2"
  }
}

#  Deploy code from a public GitHub repo
resource "azurerm_app_service_source_control" "sourcecontrol" {
  app_id             = azurerm_linux_web_app.webapp.id
  repo_url           = "https://github.com/Azure-Samples/nodejs-docs-hello-world"
  branch             = "master"
  use_manual_integration = true
  use_mercurial      = false
}

# Output the resource ID of azurerm_app_service_source_control
output "source_control_resource_id" {
  value = azurerm_app_service_source_control.sourcecontrol.id
}

Print the resource id of source control by adding the code snippet below in main.tf code:-

# Output the resource ID of azurerm_app_service_source_control
output "source_control_resource_id" {
  value = azurerm_app_service_source_control.sourcecontrol.id
}

And then import the source control latest state with the command below by using the resource id printed in the terminal with the code above.

terraform import azurerm_app_service_source_control.sourcecontrol /subscriptions/xxxxx44fb-b5ba-2b83a074c23f/resourceGroups/myResourceGroup-56454/providers/Microsoft.Web/sites/webapp-56454

As my resource is already managed by terraform it gave me the warning above.