dependabot.yml: Restricted dev dependencies to impl directory

Author: luisfi-dev

.github/dependabot.yml

@@ -15,7 +15,7 @@ updates:
 
   # Development dependencies (e.g., [dev-dependencies])
   - package-ecosystem: "cargo"
-    directory: "/"
+    directory: "impl"
     schedule:
       interval: daily
     allow: