Improve tests for Supermetrics

[angelika233]

Check te return type in /unit/test_supermetrics.py (should be a list, not dict?)
#1054 (comment)

columns = supermetrics._get_col_names_google_analytics(mock_response)
assert columns == {"ga:date": "2023-01-01", "ga:sessions": 100}

Check the response format in /unit/test_supermetrics.py, it might be pivoted
#1054 (comment)

mock_response = {
        "meta": {
            "query": {
                "fields": [
                    {"field_name": "ga:date", "field_split": "column"},
                    {"field_name": "ga:sessions", "field_split": "row"}
                ]
            }
        },
        "data": [{"ga:date1": "2023-01-01", "ga:date2": "2024-01-01", "ga:sessions": 100}]
    }