Update login paragraph in crates-io docs.

Author: fa7ca7

src/doc/crates-io.md

@@ -21,7 +21,8 @@ $ cargo login abcdefghijklmnopqrstuvwxyz012345
 ```
 
 This command will inform Cargo of your API token and store it locally in your
-`~/.cargo/config`. Note that this token is a **secret** and should not be shared
+`~/.cargo/credentials` (previously it was `~/.cargo/config`).
+Note that this token is a **secret** and should not be shared
 with anyone else. If it leaks for any reason, you should regenerate it
 immediately.