Update details about auto-cancel redundant pipelines to match docs

What does this MR do?

This MR updates the language seen when browsing in a project to Settings > CI/CD > General pipelines and looking at the details about Auto-cancel redundant pipelines.

Today, we say:

New pipelines cause older pending pipelines on the same branch to be cancelled.

However, the docs say this about Auto-cancel redundant pipelines:

You can set pending or running pipelines to cancel automatically when a new pipeline runs on the same branch.

This MR clarifies that pending and running pipelines can be canceled automatically when Auto-cancel redundant pipelines is enabled.

This discrepancy was brought to light by a customer in a ticket that is available to GitLab team members with access to ZenDesk.

Screenshots (strongly suggested)

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