Jira Connect: ensure that the Clear button is visible in the Namespace search

What does this MR do?

In the Jira Connect App, ensures that the Clear button (x button) is visible in the Namespace search. Previously, the x button was not visible (issue: #331028 (closed))

gl-search-box-by-type has internal logic that only shows the clear button when the value prop is truthy, so this MR adds the :value prop to our search box instance.

Screenshots (strongly suggested)

With Value	Loading state

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
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• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.