pw_presubmit: Fix missing comma

Fix missing comma in compatibility.json.

Bug: 328
Change-Id: Icc094bb08f14d4a3de51ec8c32c28bd4fee64185
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/34762
Pigweed-Auto-Submit: Rob Mohr <mohrr@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Reviewed-by: Wyatt Hepler <hepler@google.com>
Reviewed-by: Armando Montanez <amontanez@google.com>
diff --git a/pw_env_setup/compatibility.json b/pw_env_setup/compatibility.json
index 3c3cac7..07db79a 100644
--- a/pw_env_setup/compatibility.json
+++ b/pw_env_setup/compatibility.json
@@ -1,7 +1,7 @@
 {
   "cipd_package_files": [
     "pw_env_setup/py/pw_env_setup/cipd_setup/pigweed.json",
-    "pw_env_setup/py/pw_env_setup/cipd_setup/luci.json"
+    "pw_env_setup/py/pw_env_setup/cipd_setup/luci.json",
     "pw_env_setup/py/pw_env_setup/cipd_setup/compatibility.json"
   ],
   "virtualenv": {