Fix failing test in SourceListViewTest

[lucasmarchd01]

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FAIL: test_ordering (main_app.tests.test_views.test_source.SourceListViewTest) [Order by country, ascending]
Order is currently available by country, city + institution name (parameter:
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Traceback (most recent call last):
  File "/code/cantusdb_project/main_app/tests/test_views/test_source.py", line 1112, in test_ordering
    self.assertEqual(
AssertionError: Lists differ: [<Sou[337 chars]outh Derrick, Sit ad repellendus nihil placeat[883 chars]ab.>] != [<Sou[337 chars]outh Joseburgh, Dignissimos atque excepturi ne[883 chars]ab.>]

First differing element 3:
<Source: South Derrick, Sit ad repellendus nihil placeat[42 chars] ab.>
<Source: South Joseburgh, Dignissimos atque excepturi ne[81 chars]uia.>

Diff is 1456 characters long. Set self.maxDiff to None to see it.

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Ran 352 tests in 52.808s

FAILED (failures=1, skipped=9)

[dchiller]

I believe this will be solved when #1716 is merged (are you getting this failure intermittently?) but let's see...