Use standardized task name for validating workflows

This is the name that was chosen for the standard template for GitHub Actions workflow validation, to be used on all
Arduino tooling projects.

Author: per1234

.github/workflows/lint-config.yml

@@ -29,4 +29,5 @@ jobs:
           version: 3.x
 
       - name: Lint configuration files
-        run: task config:lint
+        run: task ci:validate
+

Taskfile.yml

@@ -331,7 +331,7 @@ tasks:
     cmds:
       - task: workflow:validate
 
-  workflow:validate:
+  ci:validate:
     desc: Validate GitHub Actions workflows against JSON schema
     vars:
       # Source: https://github.com/SchemaStore/schemastore/blob/master/src/schemas/json/github-workflow.json