Update shakapacker version in package.json to 9.0.0.beta.11

- Update spec/dummy/package.json shakapacker dependency from 8.2.0 to 9.0.0.beta.11
- This matches the Gemfile update in the previous commit

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Co-Authored-By: Claude <noreply@anthropic.com>

Author: justin808

spec/dummy/package.json

@@ -45,7 +45,7 @@
     "sass": "^1.43.4",
     "sass-loader": "^12.3.0",
     "sass-resources-loader": "^2.1.0",
-    "shakapacker": "8.2.0",
+    "shakapacker": "9.0.0.beta.11",
     "style-loader": "^3.3.1",
     "terser-webpack-plugin": "5.3.1",
     "url-loader": "^4.0.0",