Don't install yarn

src/freedombone-app-koel

@@ -693,11 +693,6 @@ function install_koel {
         fi
     fi
     npm install -g yarn
-    yarn install
-    if [ ! "$?" = "0" ]; then
-        echo $"Can't install yarn"
-        exit 682427
-    fi
     php composer.phar install
     npm install