WebSearch: unit test update

• Amends the tests test_parsing_structured_query_existing_field and test_parsing_colons_and_spaces_badly_structured to use more common fields to keep the tests from failing on some production sites due to different non-Atlantis index configurations these sites may have. (closes #1326)

• Fixes typos in test functions.

Co-authored-by: Alessio Deiana <alessio.deiana@cern.ch>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>