Update github-label-sync version in 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/sync-labels-npm.md

@@ -22,7 +22,7 @@ Add the dependencies by running this command:
 
 ```text
 npm install --save-dev ajv-cli@^5.0.0 ajv-formats@^3.0.1
-npm install --save-dev --save-exact github-label-sync@2.3.1
+npm install --save-dev --save-exact github-label-sync@3.0.0
 ```
 
 Commit the resulting changes to the `package.json` and `package-lock.json` files.