fix: add documentation to the possible values of :app in conferencing controller

[ibex088]

What does this PR do?

• Fixes #XXXX (GitHub issue number)
• Fixes CAL-XXXX (Linear issue number - should be visible at the bottom of the GitHub issue description)

Visual Demo (For contributors especially)

A visual demonstration is strongly recommended, for both the original and new change (video / image - any one).

Video Demo (if applicable):

• Show screen recordings of the issue or feature.
• Demonstrate how to reproduce the issue, the behavior before and after the change.

Image Demo (if applicable):

• Add side-by-side screenshots of the original and updated change.
• Highlight any significant change(s).

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. If N/A, write N/A here and check the checkbox.
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

How should this be tested?

• Are there environment variables that should be set?
• What are the minimal test data to have?
• What is expected (happy path) to have (input and output)?
• Any other important info that could help to test that PR

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
cal	🛑 Canceled (Inspect)			Mar 18, 2025 8:51pm
calcom-web-canary	🛑 Canceled (Inspect)			Mar 18, 2025 8:51pm

[graphite-app]

Graphite Automations

"Add consumer team as reviewer" took an action on this PR • (03/18/25)

1 reviewer was added to this PR based on Keith Williams's automation.

"Add ready-for-e2e label" took an action on this PR • (03/18/25)

1 label was added to this PR based on Keith Williams's automation.

[github-actions]

E2E results are ready!

• Workflow #52878.1 latest results