[openthread] Use openthread 1.3

Change-Id: I819250ba2353621f5e2f5073e6538ec090981233
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/openthread/+/712842
Reviewed-by: Robert Quattlebaum <rquattle@google.com>
diff --git a/etc/gn/openthread.gni b/etc/gn/openthread.gni
index 68e6ecb..e419d0d 100644
--- a/etc/gn/openthread.gni
+++ b/etc/gn/openthread.gni
@@ -70,7 +70,7 @@
 if (openthread_enable_core_config_args) {
   declare_args() {
     # Thread version: 1.1, 1.2
-    openthread_config_thread_version = "1.2"
+    openthread_config_thread_version = "1.3"
 
     # Log output: none, debug_uart, app, platform
     openthread_config_log_output = ""