Changes proposed in this Pull Request:

WC_Product::is_virtual() returns a false positive for unassembled bundle products. This PR adds a check to ensure bundle products are not hidden unless explicitly marked as hidden.

Closes #1769.

• [ x] Do the changed files pass phpcs checks? Please remove phpcs:ignore comments in changed files and fix any issues, or delete if not practical.

Detailed test instructions:

1. Start with Product Bundles and Facebook for WooCommerce connected and synced with a FB catalog;
2. Create a bundled product with the default settings — in my case I have added two simple products to the bundle;
3. In the Facebook settings for that product, switch Facebook sync to Sync and show in the catalog and save the changes
4. See that the change wasn't saved;
5. Go to Facebook's Catalog Manager > All Items (in the filters) and see that the bundled product is there but not visible
6. Switch to this branch and go back to step 4 and save
7. Observe the changes remain, and the product is now visible on Facebook's Catalog Manager

Changelog entry

Fix - Ensure bundles are not treated as virtual products on product_sync