Change description of default version example snippet to be realistic

History shows that the previous description "latest stable version of Task" is not likely to be accurate over time.
Better to just be honest about what the action does.

Author: per1234

README.md

@@ -25,7 +25,7 @@ It will be convenient to use [`${{ secrets.GITHUB_TOKEN }}`](https://docs.github
 
 ## Usage
 
-To get the latest stable version of Task just add this step:
+To get the action's default version of Task just add this step:
 
 ```yaml
 - name: Install Taskfile