fix: remove unused code

Author: MrtinoRG

convert_book/convert_to_quarto_book.py

@@ -1596,12 +1596,6 @@ def process_longtable(match):
 
     return content
 
-    # Find all longtable environments and replace them
-    pattern = r'\\begin\{longtable\}\{([^}]*)\}(.*?)\\end\{longtable\}'
-    content = re.sub(pattern, process_longtable, content, flags=re.DOTALL)
-    
-    return content
-
 
 def copy_extensions_dir(src_dir, dest_dir):
     """