module-bluetooth-proximity has not worked for quite a while, since it
uses pre-BlueZ4 APIs. Nobody complained since then, which is a good
indication that it doesn't have much users. Even the original commit
message refers to it more as a toy than as something of great use: "add
new fun module that automatically mutes your audio devices when you
leave with your bluetooth phone, and unmutes when you come back"

Removing it we completely remove the dependency on libbluetooth.