cross_toml: Include correct docs file

instead of the `cross_toml` file that has been replaced as part of this
PR.

Author: har7an

src/cross_toml.rs

@@ -1,4 +1,4 @@
-#![doc = include_str!("../docs/cross_toml.md")]
+#![doc = include_str!("../docs/config_file.md")]
 
 use crate::docker::custom::PreBuild;
 use crate::docker::PossibleImage;