Update voice-chat.md

[rbxphogen]

Changes

Update the description of the voice-chat home page to link to the audio API. Update language to note proximity chat is merely the default behavior.

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[rbitia]

In general we also need to make sure whatever code samples are given, developers could copy and paste and it would just work. So if they need to configure teams before integrating team voice chat for example a link to those steps should be in here

[rbitia]

lgtm!!