[🐛 Bug]: python code got parsed into yaml when test run

[Kiryous]

Describe the bug
If I return a dict from python step, the code is parsed into dict instead of staying string resulting in python-step error. Happens only when test running, with manual run Run now works as intended.

To Reproduce
Steps to reproduce the behavior:

1. Create workflow with the following python-step:

workflow:
  id: ede4b9cd-70be-44f1-bc19-fa7f7f87323b
  name: iterating twice
  description: iterating twice
  disabled: false
  triggers:
    - type: manual
  inputs: []
  consts: {}
  owners: []
  services: []
  steps:
    - name: python-step
      provider:
        type: python
        config: "{{ providers.default-python }}"
        with:
          code: '{"users": [{"description": "first", "user": "john.doe@gmail.com"}]}'

2. Click on Test Run
3. See error unhashable type: 'dict' and workflow definition changed, code transformed into a parsed yaml representation of dict.

Expected behavior
If run via Run now works just fine, code stays the string, the same should happen on test run.

[Kiryous]

Should be fixed in #5031