[doc] Bump Sonata version

Author: marnovandermaas

doc/getting-started.md

@@ -110,7 +110,7 @@ Nix can and will build everything from source if it can't find a cached version,
 Clone the Sonata software repository, *making sure to recursively clone submodules as well*, then navigate into it.
 
 ```sh
-git clone --branch v1.0 \
+git clone --branch v1.3 \
     --recurse-submodule \
     https://github.com/lowRISC/sonata-software.git
 cd sonata-software