chore(eas): drop the update channels (no expo-updates installed yet)

The preview/production profiles referenced channel "preview"/"production" which
requires expo-updates + `eas update:configure`. Not needed for the TestFlight
build; dropping them avoids the install prompt. (Re-add when we deliberately
wire up EAS Update / OTA.)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/rebreak-native/eas.json

@@ -29,8 +29,7 @@
       "android": {
         "buildType": "apk",
         "autoIncrement": false
-      },
-      "channel": "preview"
+      }
     },
     "production": {
       "env": {
@@ -43,8 +42,7 @@
       "android": {
         "buildType": "app-bundle",
         "autoIncrement": false
-      },
-      "channel": "production"
+      }
     }
   },
   "submit": {