Automerge: [prepare-code-coverage-artifact.py] Change run line to use python3

Author: nico

llvm/utils/prepare-code-coverage-artifact.py

@@ -1,6 +1,4 @@
-#!/usr/bin/env python
-
-from __future__ import print_function
+#!/usr/bin/env python3
 
 """Prepare a code coverage artifact.