Add missing empty line in error output of Trivia unit test

[Jackenmen]

Description of the changes

Very minor thing, the error message is missing an empty line between bullet points, here's an example:

TypeError: The following lists contain errors:
- starwars:
    YAML error:
    while scanning a simple key
      in "/home/runner/work/Red-SmileyBot/Red-SmileyBot/.tox/py38/lib/python3.8/site-packages/redbot/cogs/trivia/data/lists/starwars.yaml", line 395, column 1
    could not find expected ':'
      in "/home/runner/work/Red-SmileyBot/Red-SmileyBot/.tox/py38/lib/python3.8/site-packages/redbot/cogs/trivia/data/lists/starwars.yaml", line 396, column 1- disney:
    YAML error:
    while scanning a simple key
      in "/home/runner/work/Red-SmileyBot/Red-SmileyBot/.tox/py38/lib/python3.8/site-packages/redbot/cogs/trivia/data/lists/disney.yaml", line 1295, column 1
    could not find expected ':'
      in "/home/runner/work/Red-SmileyBot/Red-SmileyBot/.tox/py38/lib/python3.8/site-packages/redbot/cogs/trivia/data/lists/disney.yaml", line 1296, column 1

After fix it should look like this:

TypeError: The following lists contain errors:
- starwars:
    YAML error:
    while scanning a simple key
      in "/home/runner/work/Red-SmileyBot/Red-SmileyBot/.tox/py38/lib/python3.8/site-packages/redbot/cogs/trivia/data/lists/starwars.yaml", line 395, column 1
    could not find expected ':'
      in "/home/runner/work/Red-SmileyBot/Red-SmileyBot/.tox/py38/lib/python3.8/site-packages/redbot/cogs/trivia/data/lists/starwars.yaml", line 396, column 1
- disney:
    YAML error:
    while scanning a simple key
      in "/home/runner/work/Red-SmileyBot/Red-SmileyBot/.tox/py38/lib/python3.8/site-packages/redbot/cogs/trivia/data/lists/disney.yaml", line 1295, column 1
    could not find expected ':'
      in "/home/runner/work/Red-SmileyBot/Red-SmileyBot/.tox/py38/lib/python3.8/site-packages/redbot/cogs/trivia/data/lists/disney.yaml", line 1296, column 1

Have the changes in this PR been tested?

No

[leetfin]

yay I helped find a bug :aha: