Remove checks for SDK <= 21

WebRTC’s minSdk is 21, so all those checks are dead code.

Change-Id: I26497fd92259b66d9e5ac6afbb393adf4d904c77
Bug: webrtc:13780
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/253124
Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
Reviewed-by: Linus Nilsson <lnilsson@webrtc.org>
Commit-Queue: Xavier Lepaul‎ <xalep@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36140}
diff --git a/sdk/android/api/org/webrtc/SurfaceTextureHelper.java b/sdk/android/api/org/webrtc/SurfaceTextureHelper.java
index e186f9a..3ea2273 100644
--- a/sdk/android/api/org/webrtc/SurfaceTextureHelper.java
+++ b/sdk/android/api/org/webrtc/SurfaceTextureHelper.java
@@ -198,7 +198,7 @@
 
     oesTextureId = GlUtil.generateTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES);
     surfaceTexture = new SurfaceTexture(oesTextureId);
-    setOnFrameAvailableListener(surfaceTexture, (SurfaceTexture st) -> {
+    surfaceTexture.setOnFrameAvailableListener(st -> {
       if (hasPendingTexture) {
         Logging.d(TAG, "A frame is already pending, dropping frame.");
       }
@@ -208,20 +208,6 @@
     }, handler);
   }
 
-  @TargetApi(21)
-  private static void setOnFrameAvailableListener(SurfaceTexture surfaceTexture,
-      SurfaceTexture.OnFrameAvailableListener listener, Handler handler) {
-    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
-      surfaceTexture.setOnFrameAvailableListener(listener, handler);
-    } else {
-      // The documentation states that the listener will be called on an arbitrary thread, but in
-      // pratice, it is always the thread on which the SurfaceTexture was constructed. There are
-      // assertions in place in case this ever changes. For API >= 21, we use the new API to
-      // explicitly specify the handler.
-      surfaceTexture.setOnFrameAvailableListener(listener);
-    }
-  }
-
   /**
    * Start to stream textures to the given `listener`. If you need to change listener, you need to
    * call stopListening() first.