Delete line referencing v1 string (#157170)

This property would previously have been used by
ad9e4fef45/shell/platform/android/io/flutter/app/FlutterActivityDelegate.java (L59C31-L59C58)
but isn't used by the new `FlutterActivityAndFragmentDelegate`. It's also recommended to be removed by the original v1->v2 updating guide: https://github.com/flutter/flutter/blob/master/docs/platforms/android/Upgrading-pre-1.12-Android-projects.md

dev/integration_tests/android_views/android/app/src/main/AndroidManifest.xml

@@ -17,9 +17,6 @@ found in the LICENSE file. -->
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection|fontScale|screenLayout|density"
             android:hardwareAccelerated="true"
             android:windowSoftInputMode="adjustResize">
-            <meta-data
-                android:name="io.flutter.app.android.SplashScreenUntilFirstFrame"
-                android:value="true" />
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
                 <category android:name="android.intent.category.LAUNCHER" />