Fix typo in pipeline status email

What does this MR do?

This MR fixes a small typo and changes the word "succesful" to "successful".

Screenshots (strongly suggested)

[none]

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

I believe there are no risks.

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.

Security

No security risks.