Replace the android support annotation library with androidx's one.

This change does not affect downstream dependencies as androidx.annotation
is fully compatible with android.support.annotation.

Bug: webrtc:11962
Change-Id: I714b473df8d0fee8000ddf3a9beca7c5613db5ff
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/226881
Commit-Queue: Xavier Lepaul‎ <xalep@webrtc.org>
Reviewed-by: Xavier Lepaul‎ <xalep@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#34839}
diff --git a/sdk/android/api/org/webrtc/TextureBufferImpl.java b/sdk/android/api/org/webrtc/TextureBufferImpl.java
index 8d75216..31d0456 100644
--- a/sdk/android/api/org/webrtc/TextureBufferImpl.java
+++ b/sdk/android/api/org/webrtc/TextureBufferImpl.java
@@ -12,7 +12,7 @@
 
 import android.graphics.Matrix;
 import android.os.Handler;
-import android.support.annotation.Nullable;
+import androidx.annotation.Nullable;
 
 /**
  * Android texture buffer that glues together the necessary information together with a generic