Fix: Remove unused icon libraries in django-filer 3.0.0rc1

[fsbraun]

Description

Testing django-filer 3.0.0rc1 revealed that for "move file" and "delete file" an outdated, unused icon library css is requested. This leads to either a 404 or a 500 (with manifest file storage).

This PR updates the relevant templates.

Related resources

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Checklist

• [x] I have opened this pull request against master
• [x] I have added or modified the tests when changing logic
• [ ] I have followed the conventional commits guidelines to add meaningful information into the changelog
• [x] I have read the contribution guidelines and I have joined #workgroup-pr-review on Slack to find a “pr review buddy” who is going to review my pull request.

[codecov[bot]]

Codecov Report

Merging #1369 (4b20675) into master (ba24ac5) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1369   +/-   ##
=======================================
  Coverage   73.65%   73.65%           
=======================================
  Files          75       75           
  Lines        3408     3408           
  Branches      551      551           
=======================================
  Hits         2510     2510           
  Misses        727      727           
  Partials      171      171