The CI rustfmt checker uses `stable` rust, not `nightly`, but the
config options in `rustfmt.toml` only work on nightly -- on stable,
there are ignored with warnings. This means that devs running stable
get a lot of warnings and devs running nightly will accidentally format
in a way that the CI checker forbids. (specifically, using
`where_single_line`). E.g.:
```
$ cargo +stable fmt -- --check
Warning: can't set `indent_style = Block`, unstable features are only available in nightly channel.
Warning: can't set `where_single_line = true`, unstable features are only available in nightly channel.
...etc
$ cargo +nightly fmt -- --check
-where
- N: RealField,
-{
+where N: RealField {
...etc
```
Just removing the toml fixes this problem.
