[canary] Stop removing empty line in package.json (#29155)

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)