CI: Skip cells with `pip install` using regex

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.

Start by finding the tutorial CI workflow and its `jupyter nbconvert` invocation; compare it with the existing `skip-execution` tags added for #81. Check how `--RegexRemovePreprocessor` matches `!pip install ...`, then verify the CI tutorial run skips those cells while other cells still execute.

Written by the indexing model from the issue text.