Clean up third-party update temporary file

[luojiyin1987]

Part of #34067.

Summary

Register an EXIT trap for the download temporary file.
The trap removes the file on normal exit, failure, or interruption.

Root cause

The script created one file with mktemp.
It did not remove that file at the end.

Impact

The script no longer leaves its download file in the temporary directory.
The download and asset update behavior stays unchanged.

Checks

• bash -n tools/update-3rdparties.sh
• git diff --check
• A mocked download failure leaves the file with the original script.
• The same failure removes the file with the updated script.