fix: pin eslint-config-ackama to v3 (#580)

We released v4 of our config at the end of last year, which exports flat
config by default unless the `ESLINT_USE_FLAT_CONFIG` environment
variable is set to `false`.

While we want to upgrade to flat config and ESLint v9 ASAP, for now this
just pins us to v3 to get CI passing again

variants/frontend-base/js-lint/template.rb

@@ -5,7 +5,7 @@
 
 yarn_add_dev_dependencies %w[
   eslint@8
-  eslint-config-ackama
+  eslint-config-ackama@3
   eslint-plugin-node
   eslint-plugin-import
   eslint-plugin-prettier