fix usage of merge_non_contiguous_spans

brat.py

@@ -86,7 +86,7 @@ def example_to_document(
                 f"joined span parts does not match stripped span text field content. "
                 f'joined_span_texts_stripped: "{joined_span_texts_stripped}" != stripped "text": "{span_text_stripped}"'
             )
-        if not merge_non_contiguous_spans:
+        if merge_non_contiguous_spans:
             if len(starts) > 1:
                 logger.warning(
                     f"document '{doc.id}' contains a non-contiguous span (will be merged into a single span): "