Update README to point download link to 0.13.0

Author: weave-gitops-bot

README.md

@@ -51,7 +51,7 @@ use Flux already then you can easily add Weave GitOps to create a platform manag
 Mac / Linux
 
 ```console
-curl --silent --location "https://github.com/weaveworks/weave-gitops/releases/download/v0.12.0/gitops-$(uname)-$(uname -m).tar.gz" | tar xz -C /tmp
+curl --silent --location "https://github.com/weaveworks/weave-gitops/releases/download/v0.13.0/gitops-$(uname)-$(uname -m).tar.gz" | tar xz -C /tmp
 sudo mv /tmp/gitops /usr/local/bin
 gitops version
 ```