Remove nifcloud terraform provider support (it is no longer available) (#13154)

Author: yankay

.gitlab-ci/terraform.yml

@@ -106,12 +106,6 @@ tf-validate-upcloud:
     PROVIDER: upcloud
     CLUSTER: $CI_COMMIT_REF_NAME
 
-tf-validate-nifcloud:
-  extends: .terraform_validate
-  variables:
-    TF_VERSION: $TERRAFORM_VERSION
-    PROVIDER: nifcloud
-
 # tf-packet-ubuntu20-default:
 #   extends: .terraform_apply
 #   variables: