Remove npm start from Codespaces postCreateCommand (github#18193)

Author: JamesMGreene

.devcontainer.json

@@ -6,8 +6,8 @@
         "terminal.integrated.shell.linux": "/bin/bash",
         "cSpell.language": ",en"
     },
-    // Install pre-requisites, and start to serve docs.github.com locally
-    "postCreateCommand": "npm ci && npm run build && npm start",
+    // Install pre-requisites and run a build to ensure we are ready to start serving docs.github.com locally (via `npm start`)
+    "postCreateCommand": "npm ci && npm run build",
     "forwardPorts": [4000],
     // Visual Studio Code extensions which help authoring for docs.github.com.
     "extensions": [