Remove .ppd related logic and rely on CUPS to know how to print

[eaon]

On bullseye lpadmin complains that using drivers directly is deprecated,
hence we go with the flow and preemptively make sure we don't run into
this problem in the future.

This leaves printer model checks in place, but simultaneously lowers the
bar to support more printers in the future.

The change was tested with a HP LaserJet Pro M404n but not a Brother
HL-L2320D

Fixes #93

Testing

Part 1

• make test passes and the new test_get_unsupported_printer_uri is a reasonable replacement for the tests that were removed
• (Cross reference) Continue with securedrop-debian-packaging#352

Part 2

• Connect printer, to start sd-devices
• Log into client, and attempt to print a document as before
• Printing the document succeeds

[sssoleileraaa]

Part 1

• make test passes and the new test_get_unsupported_printer_uri is a reasonable replacement for the tests that were removed
• (Cross reference) Continue with securedrop-debian-packaging#352

Part 2

• Connect printer, to start sd-devices
• Log into client, and attempt to print a document as before
• ➖ Printing the document succeeds

  I am seeing issues with printing txt and image files. It can take somewhere around 5 minutes between when X Panel closes and one of these types of files is printed. They seem to print right away when I shutdown sd-devices. Doc and docx files print just fine the first time, but subsequent prints of doc and docx files never get printed. More testing is needed, but I think we should consider an alternative path where we go back to installing drivers since we're getting close to the release date.

[eaon]

Thanks @creviera, I'm glad that you caught that! Turns out that the drivers behave differently than the driver-less magic - using the drivers the printer behaves as expected, without I can reproduce your findings. I'm closing this PR in favour of opening a new one that will handle the lpadmin output in the same manner we handle the ppdc warning.