fixes composer step in phar release, this time for real, I swear!

Author: Michele Orselli

.github/workflows/build-phar.yml

@@ -40,7 +40,7 @@ jobs:
           php_version: 7.1
 
       - name: "Compile phparkitect phar"
-        run: ./bin/box.phar compile -c ./box.json
+        run: ./bin/box compile -c ./box.json
 
       - name: "Smoke test created phar"
         run : ./phparkitect.phar