adding pow example for dataframe #57419
Added example for DataFrame.pow()

- [x] closes #57419
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

I found that data format in the documentation must be '{{....}}'  not '{...}'.  
![image](https://github.com/pandas-dev/pandas/assets/31467361/0823a5e4-6422-4f97-8058-ad67a80c4657)

validation by runing command "python scripts/validate_docstrings.py pandas.DataFrame.pow"

Hope it can be helpful。 @santhoshbethi
 Thank you @dawangbaixiaofu
 https://github.com/pandas-dev/pandas/actions/runs/7942950011/job/21686768999?pr=57442 has failed due to a permission error. Can we rerun this job?

@dawangbaixiaofu could you please check this one  hi @mroeschke . Can you please check this pipeline? What am I missing here? Thanks @santhoshbethi 