roll: third_party/pigweed: third_party/mbedtls: Remove old build file

Followup to http://pwrev.dev/218709.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/220137
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 9ea805fc87d0853..ca9cf97101655f2
Roller-URL: https://ci.chromium.org/b/8743379544484027169
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ie70191cfe3f236470f3e6ad64a66a086957f845a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/220139
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 9ea805f..ca9cf97 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 9ea805fc87d085308bc966d847da31221d4bc062
+Subproject commit ca9cf97101655f24ead7adc7b041fac675d67d32