Change Dependabot directory for GitHub Actions

Dependabot is currently improperly configured so all GitHub Actions dependencies in `.github/workflows/code_checks.yml` are out of date.

> For GitHub Actions, use the value `/`. Dependabot will search the `/.github/workflows` directory, as well as the `action.yml/action.yaml` file from the root directory.

https://docs.github.com/en/code-security/reference/supply-chain-security/dependabot-options-reference#package-ecosystem

Author: cclauss

.github/dependabot.yml

@@ -7,7 +7,7 @@ updates:
       interval: "monthly"
 
   - package-ecosystem: "github-actions"
-    directory: "/.github/workflows/"
+    directory: "/"
     schedule:
       interval: "daily"
 ...