product.variants.size is never equal to zero, you have at least 1 variant...

Also, customers who have only 1 variant may still want to show the
variant title if it's not set to 'Default Title' so I am removing the
condition altogether rather than fixing it.
Revert "product.variants.size is never equal to zero, you have at least 1 variant..."

This reverts commit 3c68c5a5288214dd94e6046fbc379b3c750bcde7.
Merge branch 'master' of https://github.com/Shopify/Timber