Omit parentheses in plural labels for quick actions

What does this MR do and why?

this MR consists of changes which fixes issue #416617 (closed)

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Screenshots or screen recordings

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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.

For quick actions:

1. In an MR or issue, type in a comment: /label.

For global search (with new navigation on):

Prerequisites:

Enable elastic search, set it up from the admin, and enable the search_issue_label_aggregation feature flag. This can take a while to set up.

1. On the left sidebar, select the magnifying glass and search for something.
2. Select Issues.
3. Expand the Labels filter.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

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