gitconfig is not a toml file

Author: RalfJung

src/tools/miri/CONTRIBUTING.md

@@ -351,7 +351,7 @@ you need to pull rustc changes into Miri first, and then re-do the rustc push.
 If this fails due to authentication problems, it can help to make josh push via ssh instead of
 https. Add the following to your `.gitconfig`:
 
-```toml
+```text
 [url "[email protected]:"]
     pushInsteadOf = https://github.com/
 ```