Fixes #9953

The "working directory" arguments to "gnome-terminal" and "konsole" were incorrect due to slight mis-use of ProcessBuilder, which meant they were badly formed and the terminal loaded in a default directory (most likely the user's home dir).

There are currently no tests at all for any of this functionality at a low-level (i.e., what operating system commands are called and with what args), nor any OS-specific test filtering, etc... probably because it is significant and complex to assert a running terminal's directory, especially from a unit test. Therefore, I have intentionally not attempted to add a test because doing so would require considerable refactoring of existing tests (OpenConsoleActionTest), with not much benefit -- and it still might not be possible to truly prove a terminal opens in a particular directory anyway.

Mandatory checks

• 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.