Update unittests.yml

[vfdev-5]

Description:
This PR is to enforce our tests while using native torch tensorboard. It is related to the recent bug #878 . Once it is fixed we can merge this one.

• Removed tensorboardX to test with torch tensorboard

Check list:

• New tests are added (if a new feature is added)
• New doc strings: description and/or example code are in RST format
• Documentation is updated (if required)

[sdesrozis]

We can’t do both ? With tensorboardX and without (using torch) ?

[vfdev-5]

We can’t do both ? With tensorboardX and without (using torch) ?

To do both, we need to uninstall tensorboardX and rerun all unit tests and smoke tests.
Idea is to keep Travis CI working with TbX and GithubCI with native torch tensorboard (as it will be probably the future).