Remove shebang from nonexecutable script

Shebang should be removed from this file, because there is no point
in executing this script on its own.

src/pip/_internal/__init__.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python
 import pip._internal.utils.inject_securetransport  # noqa
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING