Bundler option to not generate rbs files

<!-- Thank you for contributing to the rubygems) repository, and specifically to the Bundler gem. Please fill in the following sections so we can process your issue as fast as possible --> ### Describe the problem as clearly as you can `bundle gem XXXX` generates rbs files. Getting sick of deleting them. Is there a config option to disable their generation? [Does not look like there is](https://bundler.io/man/bundle-gem.1.html)! ### Post steps to reproduce the problem `bundle gem foo && ls foo/sig && rm -rf foo/sig`