BUG: DataFrame.melt gives unexpected result when column "value" already exists
- [ x] closes #34731 
- [x ] tests added / passed
- [ X] passes `black pandas`
- [ x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ x] whatsnew entry

> Linting .py code
> 16
> ##[error]./pandas/core/apply.py:9:1:F401:'pandas._libs.reduction as libreduction' imported but unused
> 

should I remove this line as part of this PR? "libreduction" isn't mentioned anywhere else in the file pandas/core/apply.py , but on the other hand, its out of scope
 Can you merge master to fix CI issue? thanks @pizzathief  @pizzathief want to make a PR to enforce this deprecation?