Remove unused image-related code and dependencies

[rebeccacremona]

The carousel of registrar logos and list of "partners" was recently removed from Perma's landing and about pages.

This PR follows up and removes the remaining code and dependencies that only supported that feature.

That includes legacy "thumbnail"-related code and dependencies that haven't been in use at any point during my tenure at LIL.

I was able to remove some packages from the Docker image:

        libjpeg62-turbo-dev \
        imagemagick \
        libmagickwand-dev \

We probably want to make a similar move on the stage and prod minions after deployment.

See ENG-173.

[codecov[bot]]

Codecov Report

Attention: 7 lines in your changes are missing coverage. Please review.

Comparison is base (c5b76cf) 70.30% compared to head (e2cab71) 70.65%. Report is 9 commits behind head on develop.

Files	Patch %	Lines
perma_web/tasks/dev.py	0.00%	5 Missing :warning:
perma_web/perma/models.py	50.00%	1 Missing :warning:
perma_web/perma/views/service.py	50.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #3449 +/- ## =========================================== + Coverage 70.30% 70.65% +0.34% =========================================== Files 52 52 Lines 6729 6689 -40 =========================================== - Hits 4731 4726 -5 + Misses 1998 1963 -35 ```

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[rebeccacremona]

Thanks! I think you don't have to install libpango-1.0-0 and libcairo2: I just had to do that for the functional tests, which use playwright and chromium. I don't think you have to install any of the packages in that stanza, right?

[bensteinberg]

Ah whoops right, thanks.