Auto merge of #116962 - estebank:issue-63835, r=oli-obk

Do not bold main message in `--error-format=short`

Fix #63835.

Before:

<img width="484" alt="Screenshot 2023-10-19 at 3 52 53 PM" src="https://github.com/rust-lang/rust/assets/1606434/9bd6cbd5-a4ce-4cc3-8c5f-60a8d3ad38da">

After:

<img width="492" alt="Screenshot 2023-10-19 at 3 52 32 PM" src="https://github.com/rust-lang/rust/assets/1606434/0cf2417a-08f2-4074-860c-a88a838a4209">

Author: bors