Update prettier version in "Check Prettier Formatting" template installation docs

This is now the version used as standard in all Arduino Tooling projects, which the "template" is intended to be used
with.

Author: per1234

workflow-templates/check-prettier-formatting-task.md

@@ -34,7 +34,7 @@ The tool dependencies of this workflow are managed by [npm](https://www.npmjs.co
 Add the dependencies by running this command:
 
 ```text
-npm install --save-dev prettier@^2.8.7
+npm install --save-dev prettier@^2.8.8
 ```
 
 Commit the resulting changes to the `package.json` and `package-lock.json` files.