[jellyfin] remove non-existent pvc from README

[zer0tonin]

Special notes for your reviewer:

Just a doc fix.

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• [X] Chart Version bumped
• [X] Variables are documented in the README.md
• [X] Title of the PR starts with chart name (e.g. [radarr])