Merge pull request #553 from charafau/min_sdk_fix

fixed min sdk for android

android/src/main/AndroidManifest.xml

@@ -1,7 +1,6 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
           xmlns:tools="http://schemas.android.com/tools"
           package="com.flutter_webview_plugin">
-    <uses-sdk android:minSdkVersion="16" />
     <application>
         <provider
             android:name="androidx.core.content.FileProvider"