change: Rename web labels 'Search pre-configured' to 'Search pre-selected'

[mayank1008-tech]

Renamed the UI label "Search pre-configured" to "Search pre-selected" and "Web search fetchers" to "Pre-selected fetchers"

Closes #14557

Steps to test

1. Open JabRef.
2. Open the Web Search side panel (View -> Web search).
3. Verify that the dropdown menu now reads "Search pre-selected".
4. Go to Options -> Preferences -> Web search.
5. Verify that the section header now reads "Pre-selected fetchers".

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.

[jabref-machine]

JUnit tests of jablib are failing. You can see which checks are failing by locating the box "Some checks were not successful" on the pull request page. To see the test output, locate "Source Code Tests / Unit tests (pull_request)" and click on it.

You can then run these tests in IntelliJ to reproduce the failing tests locally. We offer a quick test running howto in the section Final build system checks in our setup guide.

[Siedlerchr]

https://devdocs.jabref.org/code-howtos/localization.html

[mayank1008-tech]

@Siedlerchr I updated localization and the Unit test - jablib also passed in my local machine.