Typo fix stoping -> stopping in the CI README.md

What does this MR do?

I noticed a typo in the CI README.md, the word "stoping" should be spelled "stopping."

I simply followed the "If you spot an error or a need for improvement and would like to fix it yourself in a merge request" link at the bottom of the documentation page (https://docs.gitlab.com/ee/ci/yaml/README.html).

What are the relevant issue numbers?

None

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.