Disable toml "parse" feature

[dtolnay]

The toml dependency is only used for serializing --config flags.

cargo-docs-rs/src/main.rs

Lines 219 to 221 in d1368f6

	let rustflags = toml::Value::try_from(&rustflags).unwrap();
	cargo_rustdoc.flag_value("--config", format!("build.rustflags={}", rustflags));
	cargo_rustdoc.flag_value("--config", format!("host.rustflags={}", rustflags));

We do not need support for parsing TOML in this crate.

Before:

$ cargo tree -e features -i toml
toml v0.8.19
├── toml feature "default"
│   └── cargo-docs-rs v0.1.13 (/git/cargo-docs-rs)
│       └── cargo-docs-rs feature "default" (command-line)
├── toml feature "display"
│   └── toml feature "default" (*)
└── toml feature "parse"
    └── toml feature "default" (*)

After:

$ cargo tree -e features -i toml
toml v0.8.19
└── toml feature "display"
    └── cargo-docs-rs v0.1.13 (/git/cargo-docs-rs)
        └── cargo-docs-rs feature "default" (command-line)