fix: laws.py added missing import logging (#3501)

### What problem does this PR solve?

_Choosing Laws Chunk Method results in an error when parsing a document.
The error is caused by a missing import in the `laws.py` file._

```
Traceback (most recent call last):
  File "/ragflow/rag/svr/task_executor.py", line 445, in handle_task
    do_handle_task(task)
  File "/ragflow/rag/svr/task_executor.py", line 384, in do_handle_task
    cks = build(r)
          ^^^^^^^^
  File "/ragflow/rag/svr/task_executor.py", line 196, in build
    cks = chunker.chunk(row["name"], binary=binary, from_page=row["from_page"],
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/ragflow/rag/app/laws.py", line 161, in chunk
    for txt, poss in pdf_parser(filename if not binary else binary,
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/ragflow/rag/app/laws.py", line 124, in __call__
    logging.debug("layouts:".format(
    ^^^^^^^
NameError: name 'logging' is not defined. Did you forget to import 'logging'

```

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [ ] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

Co-authored-by: Michal Masrna <m.marna1@gmail.com>

rag/app/laws.py

 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 #
+import logging
 from tika import parser
 import re
 from io import BytesIO