Fix the display problem of the drop-down list

What does this MR do and why?

Fix the display problem of the drop-down list in Pipelines page.

Before, no matter which item in the drop-down list was selected, when the drop-down list was expanded, the first item was selected and the corresponding icon ✓ was missing.

Screenshots or screen recordings

Before	After

How to set up and validate locally

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

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.

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cc @mtan-gitlab @lxwan