pw_thread_freertos: Add missing dep to library

Change-Id: I4c0f9a8f6658d32dc03f4c573c0c3042c4dd70b2
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/169239
Commit-Queue: Auto-Submit <auto-submit@pigweed-service-accounts.iam.gserviceaccount.com>
Reviewed-by: Armando Montanez <amontanez@google.com>
Pigweed-Auto-Submit: Ted Pudlik <tpudlik@google.com>
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
diff --git a/pw_thread_freertos/BUILD.bazel b/pw_thread_freertos/BUILD.bazel
index ff5dfef..606dc41 100644
--- a/pw_thread_freertos/BUILD.bazel
+++ b/pw_thread_freertos/BUILD.bazel
@@ -228,6 +228,7 @@
     deps = [
         "//pw_function",
         "//pw_log",
+        "//pw_span",
         "//pw_status",
         "@freertos",
     ],