[PIPE-4713] Updates [ci skip] docs

[Fernando-Abreu]

Description

This change makes it clear that we will not execute the pipeline only when the skip tag is in the last commit.

Reasons

In our docs, it says that in a multi-commit push, any commit that has the skip tag would make the whole push be skipped. However, that only applies if the last commit has the tag.

Content Checklist

Please follow our style when contributing to CircleCI docs. Our style guide is here: https://circleci.com/docs/style/style-guide-overview.

Please take a moment to check through the following items when submitting your PR (this is just a guide so will not be relevant for all PRs) 😸:

• [x] Break up walls of text by adding paragraph breaks.
• [x] Consider if the content could benefit from more structure, such as lists or tables, to make it easier to consume.
• [x] Keep the title between 20 and 70 characters.
• [x] Consider whether the content would benefit from more subsections (h2-h6 headings) to make it easier to consume.
• [x] Check all headings h1-h6 are in sentence case (only first letter is capitalized).
• [x] Is there a "Next steps" section at the end of the page giving the reader a clear path to what to read next?
• [x] Include relevant backlinks to other CircleCI docs/pages.