Fix getAssetsIndex task for ForgeGradle 1.0

[zeng-github01]

Changes

• Asset Download Fix:
  • Replaced the legacy asset downloading logic with the current Mojang API implementation.
  • This fix is backported and adapted from anatawa12/ForgeGradle-1.2.

Testing Performed

• Executed `./gradlew build and successfully

[LexManos]

Did some quick tests couple days ago and it didnt work on my end.
I've been working on a solution to things related to this. So keep an eye out.

[zeng-github01]

Did some quick tests couple days ago and it didnt work on my end. I've been working on a solution to things related to this. So keep an eye out.

I see, thanks.

I am still using the previous fixed version. However, I recently encountered an issue; since I am not familiar with FG, I haven't been able to figure out what caused it.

When executing the setup Workspace task, the index json file fails to be retrieved, indicating that the file does not found. However, the build task retrieves the json file successfully, and the former no longer throws errors after execution.