codefresh_pipeline: project_id always marked as changed

```
  # module.gw_test_cd.codefresh_pipeline.test will be updated in-place
  ~ resource "codefresh_pipeline" "test" {
        id         = "<THE-ID>"
        name       = "cloud-gateway/vault-test"
      - project_id = "<THE-PROJECT-ID>" -> null
        revision   = 5

(...)
```