FIX a bug where ascending and descending were inverted

[venkyyuvy]

Reference Issues/PRs: Fixes #15372

What does this implement/fix? Explain your changes.

swaped the ordering logic for ascending and descending ordering option.

[jnothman]

This breaks existing tests, it seems, and we would do well to have a test which ensures this behaviour

[jnothman]

Please add a test which checks that the correct order is used.

[adrinjalali]

Added a test and a whats_new entry. @venkyyuvy you'll need to do a git pull before you do any changes now :)

[adrinjalali]

O_o the iterative imputer fails to warn on rare occasions after one iteration? This needs some investigation

[venkyyuvy]

Added a test and a whats_new entry. @venkyyuvy you'll need to do a git pull before you do any changes now :)

You are amazing man! Thanks a lot.

Now I am feeling guilty to put my name for this bug fix. Can I add your name as well in the wats_new?

I have added a random seed, to see if it fixes the warning issue.

[codecov]

Codecov Report

Merging #15393 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #15393      +/-   ##
==========================================
+ Coverage   97.16%   97.16%   +<.01%     
==========================================
  Files         391      391              
  Lines       76858    76870      +12     
  Branches     8305     8306       +1     
==========================================
+ Hits        74680    74693      +13     
  Misses       2168     2168              
+ Partials       10        9       -1

Impacted Files	Coverage Δ
sklearn/impute/_iterative.py	98.51% <ø> (ø)	⬆️
sklearn/impute/tests/test_impute.py	99.66% <100%> (ø)	⬆️
sklearn/manifold/_mds.py	94.11% <0%> (+0.98%)	⬆️

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[jnothman]

Thanks @venkyyuvy