Pre-RFC: Adjust default object bounds

These are the new binaries:

before the patch (ef72938a8b9171abc5c4b463d3e8345dc0e603a6): https://queue.taskcluster.net/v1/task/GGjewXhCQeGkjn6qmT4wDA/runs/0/artifacts/public/rustc-dev-x86_64-unknown-linux-gnu.tar.gz

after the patch (8e70eb1bfc83cdc776ab0ac1cc67f75fbbe14f62): https://queue.taskcluster.net/v1/task/uTrYuVMuRdqgswFUhefSGg/runs/0/artifacts/public/rustc-dev-x86_64-unknown-linux-gnu.tar.gz