Revert "Add this."

This reverts commit 0727dcb.

Author: toots

.github/scripts/build-posix.sh

@@ -45,7 +45,7 @@ cd /tmp/liquidsoap-full/liquidsoap
 ./.github/scripts/checkout-deps.sh
 
 opam update
-opam install -y magic-mime poll
+opam install -y magic-mime
 
 cd /tmp/liquidsoap-full