[Feature Request] Upgrade gradle wrapper

[PMExtra]

I found that the gradlew is so dated, please upgrade it.

Just execute gradle wrapper or ./gradlew wrapper / ./gradlew.bat wrapper to upgrade itself.

Then commit the changes.

[PMExtra]

https://github.com/Grasscutters/Grasscutter/compare/stable...PMExtra:upgrade-gradle-wrapper?expand=1

For security purpose, I won't submit the pull request because it's hard to audit.