feat: update java web demo

upack.json

@@ -7,9 +7,9 @@
         "deploy": "adoptopenjdk/openjdk8"
     },
     "build_steps": [
-        "exec ./build.sh", "exec ./clean.sh"
+        "build.sh", "clean.sh"
     ],
-    "deploy_steps": ["exec ./deploy.sh"],
+    "deploy_steps": ["deploy.sh"],
     "main": "java -jar /app/app.jar",
     "author": "test"
 }