Specify full path to workflows in Dependabot configuration file

Dependabot supports managing GitHub Actions action dependencies of workflows.

Previously, Dependabot had an unintuitive behavior where workflows were expected to be found in the `.github/workflows/`
subfolder of the path specified via the `directory` key of the `dependabot.yml` configuration file, meaning that if you
want Dependabot to check the workflows at `/.github/workflows/`, you had to set `directory: /`.

This odd requirement has now been dropped. Even though backwards compatibility has been provided for `directory: /`
specifically, I think the configuration file is easier to understand with the full path to the workflows set, especially
in repositories (such as this one) where workflows are also present in another path.

Author: per1234

.github/dependabot.yml

@@ -6,7 +6,7 @@ updates:
   # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/assets/dependabot/README.md
   # See: https://docs.github.com/code-security/dependabot/working-with-dependabot/keeping-your-actions-up-to-date-with-dependabot
   - package-ecosystem: github-actions
-    directory: / # Check the repository's workflows under /.github/workflows/
+    directory: /.github/workflows/
     schedule:
       interval: daily
     labels:

workflow-templates/assets/dependabot/dependabot.yml

@@ -6,7 +6,7 @@ updates:
   # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/assets/dependabot/README.md
   # See: https://docs.github.com/code-security/dependabot/working-with-dependabot/keeping-your-actions-up-to-date-with-dependabot
   - package-ecosystem: github-actions
-    directory: / # Check the repository's workflows under /.github/workflows/
+    directory: /.github/workflows/
     schedule:
       interval: daily
     labels: