TST: verify numpy.ravel works on a list of DataFrames with specified column names (#26247)
- [x] closes  #26247
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] whatsnew entry

Inserted test to verify that np.ravel can be used on DataFrames with specified column names.