Double-click onto PDF in file list just open the file

[mohit038-zz]

Fixes #7465

when a file associated to an entry under the 'General' tab is double-clicked, a prompt opens which asks for changing the file location, description or type.

In this fix,When a file is double-clicked, it just open the file.
User can now access that prompt through a new right-click > Edit option.

• 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 documentation: Is the information available and up to date? If not created an issue at https://github.com/JabRef/user-documentation/issues or, even better, submitted a pull request to the documentation repository.