Fix some warnings seen after the migration to JDK 11

shell/platform/android/io/flutter/embedding/android/DrawableSplashScreen.java

@@ -23,6 +23,7 @@
  *
  * @deprecated
  */
+@Deprecated
 public final class DrawableSplashScreen implements SplashScreen {
   private final Drawable drawable;
   private final ImageView.ScaleType scaleType;

shell/platform/android/io/flutter/embedding/android/SplashScreen.java

@@ -23,6 +23,7 @@
  *
  * @deprecated
  */
+@Deprecated
 public interface SplashScreen {
   /**
    * Creates a {@code View} to be displayed as a splash screen before Flutter renders its first

shell/platform/android/io/flutter/view/AccessibilityBridge.java

@@ -2692,7 +2692,7 @@ private SpannableString createSpannableString(String string, List<StringAttribut
           switch (attribute.type) {
             case SPELLOUT:
               {
-                final TtsSpan ttsSpan = new TtsSpan.Builder(TtsSpan.TYPE_VERBATIM).build();
+                final TtsSpan ttsSpan = new TtsSpan.Builder<>(TtsSpan.TYPE_VERBATIM).build();
                 spannableString.setSpan(ttsSpan, attribute.start, attribute.end, 0);
                 break;
               }