Adjust wording on troubleshooting step for Code Quality docs

What does this MR do?

The troubleshooting section of this doc uses "default" rather than "target" when stating that the Code Quality widget may not appear if the target branch does not have any Code Quality artifacts.

This can (and has) led users to believe that the default branch requires previous Code Quality jobs with artifacts present in order for the widget to load, even if the default branch isn't the target for the merge request. However, its the target branch for the MR that needs to have these jobs present, which isn't always the default branch.

This MR simply adjusts the wording to use "target" rather than "default" on this line.

Related issues

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