Small issue on Upgrade.md that prevents dependency installation

[miguelingka]

Describe the bug
The upgrade guide should be correctly updated about the unirest java dependency. Currently points to a non existing version.

https://github.com/Kong/unirest-java/blob/main/UPGRADE_GUIDE.md?plain=1#L42

This line should be updated to have java-core instead of just java.

To Reproduce
Steps to reproduce the behavior:

1. Follow the documentation regarding the version 4 installation
2. Get an error when trying to update maven dependencies

Expected behavior
Dependency is correctly instaled.

Screenshots

Environmental Data:

• 11
• Version 4.*

[ryber]

thanks! Fixed