…pe column (pandas-dev#47757)

* Update test_melt.py

* Update v1.5.0.rst

* Update melt.py

* Update test_melt.py

* Update melt.py

* fix type

* Update doc/source/whatsnew/v1.5.0.rst

Co-authored-by: Matthew Roeschke <emailformattr@gmail.com>

* Update melt.py

* Update test_melt.py

Co-authored-by: Matthew Roeschke <emailformattr@gmail.com>