simplify CI horovod

[Borda]

What does this PR do?

after #4941 we shall have a path to the root so the local setting shall not be needed...

Before submitting

• Was this discussed/approved via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure your PR does only one thing, instead of bundling different changes together? Otherwise, we ask you to create a separate PR for every change.
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?
• Did you verify new and existing tests pass locally with your changes?
• If you made a notable change (that affects users), did you update the CHANGELOG?

PR review

Anyone in the community is free to review the PR once the tests have passed.
Before you start reviewing make sure you have read Review guidelines. In short, see the following bullet-list:

• Is this pull request ready for review? (if not, please submit in draft mode)
• Check that all items from Before submitting are resolved
• Make sure the title is self-explanatory and the description concisely explains the PR
• Add labels and milestones (and optionally projects) to the PR so it can be classified; Bugfixes should be including in bug-fix release milestones (m.f.X) and features should be included in (m.X.b) releases.

Did you have fun?

Make sure you had fun coding 🙃

[codecov]

Codecov Report

Merging #4951 (b5de45d) into master (b00991e) will increase coverage by 3%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #4951    +/-   ##
=======================================
+ Coverage      90%     93%    +3%     
=======================================
  Files         129     129            
  Lines        9372    9372            
=======================================
+ Hits         8423    8689   +266     
+ Misses        949     683   -266     

[tchaton]

@Borda It seems to broke some tests.

[Borda]

@Borda It seems to broke some tests.

true but it strange that it works on GPU fine :]

[Borda]

ok, I found the problem, Conda env do not use PYTHONPATH so the PL path is missing...
this basically means that all our tests with DDP will/may fail if they run on Conda... @tchaton