fix(jabgui): focus to link field whe open dialog

[nothiaki]

Closes #13486

focus to link field when open LinkedFileEditDialog

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• Change in CHANGELOG.md described in a way that is understandable for the average user (if change is visible to the user)
• Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (if change is visible to the user)
• [/] 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.

[trag-bot]

@trag-bot didn't find any issues in the code! ✅✨

[koppor]

@calixtus This is differrent than the stack overflow solution from https://stackoverflow.com/a/70021819/873282 - is it also OK?

[koppor]

DevCall: @nothiaki Please follow https://stackoverflow.com/a/70021819/873282 if you can.

[koppor]

Reason: lifecycle could be "problematic" - there is no guarantee that intializate is called right before showing the dialog.

[jabref-machine]

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[koppor]

Other contributor works in this now.

[koppor]

The reason for the double work is that @nothiaki did not follow our contributing guide to get a task assigned: https://github.com/JabRef/jabref/blob/main/CONTRIBUTING.md#getting-a-task-assigned