CI Workflow: Update sphinx-intl new release & Install Transifex CLI.

[AhmedBasem20]

CLoses #5748

The new sphinx-intl release (2.1.0) is now updated, Also Transfix CLI installation script has been added.

[unkcpz]

Thanks for the contribution @AhmedBasem20, just one minor request. Can you also add a version for the transifex cli as mentioned in https://github.com/transifex/cli#installing-with-a-script-linuxmac?

I think there is some problem on my initial implementation, since I now realize it is not a good practice to push to transifex when new version released. The documentation .pot files need to updated when there are new changes in /doc folder in the main branch, which will make the latest of other language versions of documentation synchronize with the latest official version.
But nothing related to this PR, and I'll leave it to myself in the future.

[AhmedBasem20]

Thanks @unkcpz for reviewing. I added the requested transifex cli version. Your insight on best practices is greatly appreciated. Thanks again for your time and guidance!

[unkcpz]

Thanks @AhmedBasem20. I give it a local test, all good!