Closes #12530

Remove the Close Library menu item from File menu. Remove the shortcut Ctrl + W from tab's context menu and set it in org.jabref.gui.frame.JabRefFrame#initKeyBindings instead.

Steps to test

1. Open at least 2 tabs.
2. Choose randomly a tab, except the first one. Press Ctrl + W and the current tab should be closed.
3. Right-click randomly a tab and click Close Library. The tab should be closed regardless whether it is the current tab.

Short video showing step 3.

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• I manually tested my changes in running JabRef (always required)
• [/] I added JUnit tests for changes (if applicable)
• I added screenshots in the PR description (if change is visible to the user)
• I described the change in CHANGELOG.md in a way that is understandable for the average user (if change is visible to the user)
• I checked the user 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 updating file(s) in https://github.com/JabRef/user-documentation/tree/main/en.