Removed old manual import in the shell

[raffaellasuardini]

Changes in this pull request:

I removed the following lines since in Django 5.2 has the automatic import for shell so there is no need to import the model

>>> from blog.models import Post

[ekohl]

Since we updated in 5132e10 to 5.2, this should be OK. I didn't verify it myself, but trusting it based on the linked release note.