Update existing Django model by deleting URL fields

[benpinhassi]

fixes #197 Hey, I deleted the variables from the file manage.py Regarding the requested columns for removal: github_primary_url - URLField slack_url - URLField google_drive_url - URLField hfla_website_url - URLField readme_url - URLField wiki_url - URLField

• The variable github_primary_url was defined as CharField and not URLField. I deleted it but I can undo it.
• I didn't change the fixture model or test case because we deleted the URLs only.
• I also deleted the connected fields on the file serializers.py
• I ran ./scripts/test.sh and ./scripts/precommit-check.sh successfully.

I hope this is what you mean by updating the model. If not I'll make the necessary changes.

[fyliu]

I don't think I can review this yet. There's still decisions to be made on what to delete.

It's in #78 in the question column.

[fyliu]

@Neecolaa confirmed that the requirements are good, so I can review this.