FIx Preferences window cannot 'outgrow' scrollbar

[qingyacanxue]

Fixes #9017 Preferences window cannot 'outgrow' horizontal scrollbar #9017, a UI bug
And the changing result screen shot is provided in the issue
link: #9017

• Change in CHANGELOG.md described in a way that is understandable for the average user (if applicable)
• Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (for UI changes)
• Checked developer's documentation: Is the information available and up to date? If not, I outlined it in this pull request.
• Checked documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request to the documentation repository.

[qingyacanxue]

The descirption of the PR was missing and I may describe it again. It is an UI bug with link: #9017
The changing result screen shot is provided in the issue, please go to see it and tell me if you have other requirements.

[calixtus]

Thanks for your contribution and your interest in JabRef.
Yet i'm not so happy with your solution, as it is more a workaround then a fix, as this problem might also occur in other tabs as well. Maybe you could just reduce the size of the slider pane just a bit, so the controls inside the tab can still upsize as the like without outgrowing the windows?