Fix referenced Dockerfile line numbers (#5)

Author: shamouda

README.md

@@ -13,10 +13,10 @@ Currently, the MMTk team run the development and testing of MMTk and bindings on
 
 As in [Dockerfile](https://github.com/mmtk/mmtk-dev-env/blob/main/Dockerfile), setting up the dependencies can be done through these steps:
 
-1. Install the required packages: [Dockerfile#17](https://github.com/mmtk/mmtk-dev-env/blob/main/Dockerfile#L17),
-2. Install `rustup` and add it to `PATH`: [Dockerfile#20-21](https://github.com/mmtk/mmtk-dev-env/blob/main/Dockerfile#L20-L21),
-3. Install our currently used nightly Rust toolchain using `rustup`: [Dockerfile#25](https://github.com/mmtk/mmtk-dev-env/blob/main/Dockerfile#L25),
-4. Add the `i686-unknown-linux-gnu` target to the Rust toolchain: [Dockerfile#26](https://github.com/mmtk/mmtk-dev-env/blob/main/Dockerfile#L26)
+1. Install the required packages: [Dockerfile#17](https://github.com/mmtk/mmtk-dev-env/blob/main/Dockerfile#L18),
+2. Install `rustup` and add it to `PATH`: [Dockerfile#24-25](https://github.com/mmtk/mmtk-dev-env/blob/main/Dockerfile#L24-L25),
+3. Install our currently used nightly Rust toolchain using `rustup`: [Dockerfile#29](https://github.com/mmtk/mmtk-dev-env/blob/main/Dockerfile#L29),
+4. Add the `i686-unknown-linux-gnu` target to the Rust toolchain: [Dockerfile#30](https://github.com/mmtk/mmtk-dev-env/blob/main/Dockerfile#L30)
 
 __NOTE:__ We successfully tried the same procedure on Ubuntu-20.04, but Ubuntu-18.04 is still the version we use daily.