Add comment to not change debugJNI

[ThadHouse]

https://github.com/wpilibsuite/vscode-wpilib/blob/main/vscode-wpilib/resources/gradle/java/build.gradle#L47

That flag is shared between desktop and roborio. So if you set that flag to true, you'll deploy debug artifacts. Which would be very bad. Add some comments to not change it unless you know what you're doing.