save to blend_adjust too

[peterdudfield]

Pull Request

Description

Save blend adjusted results too, just for national

Helps with https://github.com/openclimatefix/client-private/issues/186

How Has This Been Tested?

• Ci tests
• ran locally, not noticeably longer
• checked results match nowcasting_datamodel current blend results, with and without adjuster

Checklist:

• My code follows OCF's coding style guidelines
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked my code and corrected any misspellings