Update packages/ dependencies together (#793)

This is not clearly documented, but should work:
https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#directory
dependabot/dependabot-core#2178

.github/dependabot.yml

@@ -9,10 +9,6 @@ updates:
         update-types:
           - "version-update:semver-major"
   - package-ecosystem: npm
-    directory: packages/web-features
-    schedule:
-      interval: daily
-  - package-ecosystem: npm
-    directory: packages/compute-baseline
+    directory: packages/
     schedule:
       interval: daily