Fix typo in PR template (add missing 'to')

[rgrace9]

This PR fixes a small typo in the pull request template.
The sentence “modify the above text fit your PR” was corrected to “modify the above text to fit your PR” for clarity

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.

[github-actions]

Hey @rgrace9!

Thank you for contributing to JabRef! Your help is truly appreciated ❤️.

We have automatic checks in place, based on which you will soon get automated feedback if any of them are failing.
We also use TragBot with custom rules that scans your changes and provides some preliminary comments, before a maintainer takes a look.
TragBot is still learning, and may not always be accurate.
In the "Files changed" tab, you can go through its comments and just click on "Resolve conversation" if you are sure that it is incorrect, or comment on the conversation if you are doubtful.

Please re-check our contribution guide in case of any other doubts related to our contribution workflow.

[jabref-machine]

Your pull request needs to link an issue correctly.

To ease organizational workflows, please link this pull request to the issue by including a supported keyword in the pull request's description as per syntax described in GitHub's documentation.

Examples

• ✅ Fixes #xyz links pull-request to issue. Merging the PR will close the issue.
• ✅ Fixes https://github.com/JabRef/jabref/issues/xyz links pull-request to issue. Merging the PR will close the issue.
• ✅ Fixes https://github.com/Koppor/jabref/issues/xyz links pull-request to issue. Merging the PR will close the issue.
• ❌ Fixes [#xyz](https://github.com/JabRef/jabref/issues/xyz) links pull-request to issue. Merging the PR will NOT close the issue.

[subhramit]

Thanks!