Adding platform line to compose

[dkolkena]

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What does this PR do?

Addresses https://github.com/coralproject/talk/issues/4336, ensuring that the currently supported platform is defaulted to on all machines regardless of host architecture.

These changes will impact:

• [ ] commenters
• [ ] moderators
• [ ] admins
• [x] developers

What changes to the GraphQL/Database Schema does this PR introduce?

None

Does this PR introduce any new environment variables or feature flags?

Nope

If any indexes were added, were they added to INDEXES.md?

N/A

How do I test this PR?

Pull the changes and run docker-compose up from an Apple M1 machine.

Where any tests migrated to React Testing Library?

No

How do we deploy this PR?

No changes should be necessary

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[dkolkena]

See https://vmproduct.atlassian.net/browse/CPSRE-1304?focusedCommentId=129709 for further details.

[dkolkena]

Please ignore the stray reverted commit, that was for a different PR. This is now in the correct state and ready to be reviewed.