Fix Issue #34923: Inferred dtype at the end of df explode method
- [ ] closes #34923 
- [ ] tests added / passed
          pandas/tests/frame/methods/test_explode.py, method test_inferred_dtype
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry
