Episode pages without audio log a Canvas error

Problem/Motivation

The full content template asks for delta 0 of the Audio field, so every view of an episode with no audio logs:

Requested delta 0 for unlimited cardinality field, but only deltas [0, -1] exist.

Steps to reproduce

1. Apply the recipe on Varbase Starter.
2. Create an episode with no audio.
3. Open it.
4. Check Recent log messages.

Proposed resolution

Drop the fixed delta from the player's audio expression in canvas.content_template.node.podcast.full.yml.

Remaining tasks

• ✅ File an issue
• ✅ Addition/Change/Update/Fix
• ❌ Testing to ensure no regression
• ➖ Automated unit/functional testing coverage
• ➖ Developer Documentation support
• ➖ User Guide Documentation support
• ➖ UX/UI designer responsibilities
• ➖ Accessibility and Readability
• ❌ Reviewed by a human
• ❌ Code review by maintainers
• ❌ Full testing and approval
• ❌ Credit contributors
• ❌ Review with the product owner
• ❌ Update Release Notes
• ❌ Release

Release notes snippet

• fix: #3625561 Episode pages without audio log a Canvas error.

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