add rustup update instructions

steps/1/README.md

@@ -65,6 +65,8 @@ cargo +nightly clippy
 cargo test
 ```
 
+In general, you should make sure your rust compiler is up to date with `rustup update`.
+
 It may take a while for this to complete based on how powerful your computer is.
 
 Feel free to move onto the next steps while these checks are compiling.

steps/2/README.md

@@ -6,6 +6,8 @@ This is the starting template for: https://github.com/shawntabrizi/substrate-col
 
 Follow [these installation instructions](https://docs.substrate.io/install/) to set up your development environment to work with the `polkadot-sdk`.
 
+If you have already set up your computer for the `polkadot-sdk`, you should make sure your rust compiler is up to date with `rustup update`.
+
 ### test
 
 To check that your code compiles successfully at each step, you can run: