pigweed.json: Exclude patches.json from formatting

Changes containing patches.json files are not submittable, so their
formatting doesn't really matter. Skip them in formatting checks so
developers don't get errors that they're formatted incorrectly.
(Developers will need to remove patches.json files before submission.)

Bug: b/232234662
Change-Id: I5802a6cf59740441c18a25b5d447cadaabd64b1f
Reviewed-on: https://pigweed-review.googlesource.com/c/open-dice/+/174250
Pigweed-Auto-Submit: Rob Mohr <mohrr@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed-service-accounts.iam.gserviceaccount.com>
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Darren Krahn <dkrahn@google.com>

pigweed.json

diff --git a/pigweed.json b/pigweed.json
index e5184f5..72b5934 100644
--- a/pigweed.json
+++ b/pigweed.json
@@ -13,7 +13,8 @@
         "python_formatter": "black",
         "exclude": [
           "third_party/.*/src",
-          "third_party/boringssl/err_data.c"
+          "third_party/boringssl/err_data.c",
+          "^patches\\.json$"
         ]
       }
     },