request_path had Computed enabled which prevented updating it to an empty value
TF_ACC=1 go test ./builtin/providers/azurerm -v -run TestAccAzureRMLoadBalancerProbe -timeout 120m
=== RUN TestAccAzureRMLoadBalancerProbe_basic
--- PASS: TestAccAzureRMLoadBalancerProbe_basic (119.63s)
=== RUN TestAccAzureRMLoadBalancerProbe_removal
--- PASS: TestAccAzureRMLoadBalancerProbe_removal (122.50s)
=== RUN TestAccAzureRMLoadBalancerProbe_update
--- PASS: TestAccAzureRMLoadBalancerProbe_update (129.98s)
=== RUN TestAccAzureRMLoadBalancerProbe_duplicate
--- PASS: TestAccAzureRMLoadBalancerProbe_duplicate (115.22s)
=== RUN TestAccAzureRMLoadBalancerProbe_updateProtocol
--- PASS: TestAccAzureRMLoadBalancerProbe_updateProtocol (127.25s)
PASS
ok github.com/hashicorp/terraform/builtin/providers/azurerm 614.657s