Remove expo-speech-recognition plugin from app.json

The package was removed in commit d9fff44 but the plugin
entry was left in app.json, causing EAS Build to fail with
'Unknown error in Read app config' phase.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app.json

@@ -69,13 +69,6 @@
             "backgroundColor": "#000000"
           }
         }
-      ],
-      [
-        "expo-speech-recognition",
-        {
-          "microphonePermission": "WellNuo needs access to your microphone for voice commands.",
-          "speechRecognitionPermission": "WellNuo uses speech recognition to convert your voice to text."
-        }
       ]
     ],
     "experiments": {