Fix #1013 -- Set correct icon name for audio types

[oliverroick]

Proposed changes in this pull request

• Fixes Icon lookups for audio files fail #1013: Set the correct icon file name for audio files which are not mp3 or mp4. I uploaded the corresponding icon to S3.

When should this PR be merged

Anytime.

Risks

None.

Follow up actions

None.

Checklist (for reviewing)

General

• Is this PR explained thoroughly? All code changes must be accounted for in the PR description.
• Is the PR labeled correctly? It should have the migration label if a new migration is added.
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Functionality

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Code

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Tests

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Documentation

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• Are reusable components documented? If this PR introduces components that are relevant to other developers (for instance a mixin for a view or a generic form) they should be documented in the Wiki.

[linzjax]

Ah yeah this makes a lot of sense.

[bjohare]

Looks good to me.