Fix docker compose build failure on macOS

The dockerfile path was incorrect, causing builds to fail with
'git-version.h: not found'. Changed to use docs/tutorial/Dockerfile
which is the intended Dockerfile for the tutorial.

Author: jashGi

docs/tutorial/docker-compose.yml

@@ -1,7 +1,7 @@
 x-node: &node
   build:
     context: ../..
-    dockerfile: Dockerfile
+    dockerfile: docs/tutorial/Dockerfile
     tags:
       - pg_auto_failover:tutorial
   volumes:
@@ -18,7 +18,6 @@ x-node: &node
     - 5432
 
 services:
-
   app:
     build:
       context: .