Add 'manual' to the CANCELABLE_STATUSES constant"

What does this MR do and why?

This MR adds :manual as a cancelable status to Ci::Pipeline::CANCELABLE_STATUSES and Ci::Bridge::CANCELABLE_STATUSES and CommitStatus::CANCELABLE_STATUSES through Ci::HasStatus.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. open rails console $gdk rails c
2. Observe that Ci::Pipeline::CANCELABLE_STATUSES and Ci::Bridge::CANCELABLE_STATUSES and CommitStatus::CANCELABLE_STATUSES include :manual in the array of returned statuses

Related to #460256 (closed)