Android : Xamarin not start AVD after update 5.5

My Xamarin not start after app has been updated to versio 5.5. The following warning appears:

Warning XA4211: AndroidManifest.xml //uses-sdk/@android:targetSdkVersion '15' is less than $(TargetFrameworkVersion) 'v4.5'. Using API-L for ACW compilation. (XA4211)

My AndroidManifest.xml:

<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="1" android:versionName="1.0" package="MyApp_App.MyApp_App">
<uses-sdk android:minSdkVersion="15" android:targetSdkVersion="15" />
<application android:label="MyApp" android:icon="@drawable/icon"></application>
<uses-permission android:name="android.permission.INTERNET" />