Fix multilingual .env embedding dimension

[bartschuller]

Description

This adds a neccessary line to the multilingual environment file to set the correct embedding dimension for the model configured.

How Has This Been Tested?

Using the environment without the extra setting led to indexing problems (HTTP 400 errors from Vespa, "Expected 768 values, but got 384" in the background log. With the setting, this all went away and Danswer started working.

Accepted Risk

[Any know risks or failure modes to point out to reviewers]

Related Issue(s)

My comment on issue #1204 helped at least one person.

Checklist:

• [ ] All of the automated tests pass
• [ ] All PR comments are addressed and marked resolved
• [ ] If there are migrations, they have been rebased to latest main
• [ ] If there are new dependencies, they are added to the requirements
• [ ] If there are new environment variables, they are added to all of the deployment methods
• [ ] If there are new APIs that don't require auth, they are added to PUBLIC_ENDPOINT_SPECS
• [ ] Docker images build and basic functionalities work
• [ ] Author has done a final read through of the PR right before merge