bug 1888223: remove priority from protected data access request link

[willkg]

To test, do this:

1. build socorro and then make run
2. go to http://localhost:8000/documentation/protected_data_access/
3. click on link to request protected data access
4. make sure the priority isn't set to P3--it should be --

[smarnach]

I tried following the testing instructions, but I was held up by this typo in the Makefile: #6564

[biancadanforth]

R+ once the typo from #6564 was fixed it worked for me.

[smarnach]

I followed the test instructions, and on the "New bug" page in Bugzilla I get to when clicking the link there isn't any priority field. So I can't really verify that it's set to "--" since it's just not there. But the priority is definitly gone from the query parameters, so I guess it's fine.

[willkg]

When I create the bug, it looks like this:

I bet you have advanced fields hidden. That'll make it look like this:

[willkg]

Thank you both for reviewing and fixing that make run issue!