Simplify test suite

[svlandeg]

Description

Simplify test suite to make it less dependent on the actual answers from the LLM.

• Removed unnecessary label "DESTINATION" from the NER tests
• Updated the "multiple-entities-with-same-string" Paris test (too difficult for the LLM to get right)
• Updated the "correct prediction" test to be more simple & robust against odd LLM answers
• Updated the "comma" test to be more robust

Also changed "xx" everywhere to "en" when we're testing on English sentences.

Corresponding documentation PR

NA

Types of change

test suite

Checklist

• I confirm that I have the right to submit this contribution under the project's MIT license.
• I ran all tests in tests and usage_examples/tests, and all new and existing tests passed. This includes
  • all external tests (i. e. pytest ran with --external)
  • all tests requiring a GPU (i. e. pytest ran with --gpu)
• My changes don't require a change to the documentation, or if they do, I've added all required information.