There's no feature to delete content translations on eZ Platform 1.7.
Here's how to verify the issue:
1. On a fresh installation of eZ Platform 1.7, start by creating a second language and clear the symfony cache.
2. Then create a new content with 2 different translations.
3. Now try to remove one of the translation. The feature is missing.
To go around that we need to remove and create the content again with the desired expected translations, which requires a lot of work.