docs: Update speaker_layout enum values

A documentation update was missed. Bring these values up to date with
the current reality.

docs/sphinx/reference-libobs-media-io.rst

@@ -264,10 +264,7 @@ Audio Handler
    - SPEAKERS_4POINT0
    - SPEAKERS_4POINT1
    - SPEAKERS_5POINT1
-   - SPEAKERS_5POINT1_SURROUND
    - SPEAKERS_7POINT1
-   - SPEAKERS_7POINT1_SURROUND
-   - SPEAKERS_SURROUND
 
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