CI: Skip cells with `pip install` using regex

[johnnv1]

At #81 I speed up the tutorials run CI by some minutes skipping the cells with !pip install ....

At #81, it was done by adding the tag skip-execution to the cells. But we should have some more generic/automatic way to skip these cells. Which I believe can be achieved using --RegexRemovePreprocessor option from jupyter nbcovert command.