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/IceCandidate.java b/sdk/android/api/org/webrtc/IceCandidate.java
index 03725cc..5f00b2a 100644
--- a/sdk/android/api/org/webrtc/IceCandidate.java
+++ b/sdk/android/api/org/webrtc/IceCandidate.java
@@ -10,7 +10,7 @@
 
 package org.webrtc;
 
-import android.support.annotation.Nullable;
+import androidx.annotation.Nullable;
 import java.util.Arrays;
 import org.webrtc.PeerConnection;