[canary] Stop removing empty line in package.json

This for some reason only started being an issue now, but basically we
have to make sure that an empty line is left at the end of
`package.json`, otherwise we get presubmit failures.

Resolves brave/brave-browser#46229

Author: cdesouza-chromium

tools/cr/brockit.py

@@ -1044,6 +1044,7 @@ def _update_package_version(self):
             self.target_version)
         with open(versioning.PACKAGE_FILE, "w") as package_file:
             json.dump(package, package_file, indent=2)
+            package_file.write("\n")
 
         repository.brave.run_git('add', versioning.PACKAGE_FILE)