remove slice-timing correction

[psadil]

Closes #998 by removing ability to correct for slice-timing (which had only worked for some acquisitions)

[psadil]

I'm not confident, but I think those failures are caused by changes outside this request. Perhaps I should have started from the last release rather than the master branch?

[oesteban]

Thanks much for this. Can you please rebase to upstream/master? The errors should be fixed now.

Let's see if the tests indeed pass. When merged, please do not forget to add your info to https://github.com/nipreps/mriqc/blob/master/.maint/CONTRIBUTORS.md, in case you wish so.

[welcome]

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