Install documentation update

Author: wleczny

website/docs/_advanced_install.mdx

@@ -139,7 +139,7 @@ This method is provided and supported by the community, not the core team of Sca
 Scala CLI can be installed with [Nix](https://nixos.org) with
 
 ```bash
-nix-env -iA scala-cli
+nix-env -iA nixpkgs.scala-cli
 ```
 
 </TabItem>
@@ -303,14 +303,10 @@ brew install Virtuslab/scala-cli/scala-cli
 This method is provided and supported by the community, not the core team of Scala CLI
 :::
 
-:::info
-Please note that the `arm64` architecture is not yet supported with this method.
-:::
-
 Scala CLI can be installed via [Nix](https://nixos.org) with:
 
 ```bash
-nix-env -iA scala-cli
+nix-env -iA nixpkgs.scala-cli
 ```
 
 </TabItem>