Remove unused tor_apt_repo_url override

[eloquence]

This was overlooked in the migration away from tor-apt.freedom.press
in #4080. It's harmless but unnecessary and potentially confusing.

Status

Ready for review

Deployment considerations

None, should be a noop since the variable is never used.

[codecov-io]

Codecov Report

Merging #4655 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #4655   +/-   ##
========================================
  Coverage    82.67%   82.67%           
========================================
  Files           45       45           
  Lines         3122     3122           
  Branches       338      338           
========================================
  Hits          2581     2581           
  Misses         454      454           
  Partials        87       87

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