Use bundle config path instead of bundle install --path in Ruby 2.7 on our CI

While !552 (merged) updated the Ruby version used in our CI, bundle commands are still stale as follows:

$ bundle install --jobs=$(nproc) --path=vendor --retry=3 && bundle check
[DEPRECATED] The `--path` flag is deprecated because it relies on being remembered across bundler invocations, which bundler will no longer do in future versions. Instead please use `bundle config set --local path 'vendor'`, and stop using this flag

On CI, we cannot see it since --quiet option is specified there.