pw_thread_freertos: apply pw_thread_embos style changes

Change-Id: Ic85ef57b089e4f83d73e994c613b3b01d2be4107
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/45423
Reviewed-by: Keir Mierle <keir@google.com>
Pigweed-Auto-Submit: Ewout van Bekkum <ewout@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/pw_thread_freertos/BUILD.gn b/pw_thread_freertos/BUILD.gn
index 7071804..742a1e2 100644
--- a/pw_thread_freertos/BUILD.gn
+++ b/pw_thread_freertos/BUILD.gn
@@ -104,6 +104,7 @@
   public_deps = [
     ":config",
     "$dir_pw_assert",
+    "$dir_pw_string",
     "$dir_pw_third_party/freertos",
     "$dir_pw_thread:id",
     "$dir_pw_thread:thread.facade",