[dashboard] Rename "patch" to "pull request"

[bmispelon]

In concert with https://code.djangoproject.com/ticket/35894#ticket and django/code.djangoproject.com#224, the word "patch" also needs to change on the dashboard.

[bmispelon]

I think that just needs to be fixed in the database, there are no code changes needed for this.

[marksweb]

I think that just needs to be fixed in the database, there are no code changes needed for this.

Yeah I can't see anything in the project.

[bmispelon]

I realized that there was fixture data that needed to be updated, and that it would be easier to deploy this if the rename was packaged as a data migration.

So I opened a PR that does just this: #1729