fix(combobox): do not refresh the virtualized panel every time the drop down menu is opened

[ramezgerges]

GitHub Issue (If applicable): closes #20326

PR Type

What kind of change does this PR introduce?

What is the current behavior?

What is the new behavior?

PR Checklist

Please check if your PR fulfills the following requirements:

• Docs have been added/updated which fit documentation template (for bug fixes / features)
• Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Validated PR Screenshots Compare Test Run results.
• Contains NO breaking changes
• Associated with an issue (GitHub or internal) and uses the automatic close keywords.
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Other information

Internal Issue (If applicable):

[unodevops]

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[ajpinedam]

Good

[unodevops]

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[ramezgerges]

/azp run

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Azure Pipelines successfully started running 2 pipeline(s).

[unodevops]

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[unodevops]

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[unodevops]

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[unodevops]

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[unodevops]

⚠️⚠️ The build 166928 has failed on Uno.UI - CI.