[roll third_party/pigweed] pw_protobuf: Remove codegen.h

Removes the no-longer needed codegen.h file.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/55508

third_party/pigweed Rolled-Commits: 671d13532014dd3..5fbfd88c5885f19
Roller-URL: https://ci.chromium.org/b/8839973382239160785
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8839973382239160785
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ia37191fa023f3062a6807c3f2f1ce5ee1e49b25a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/55820
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 671d135..5fbfd88 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 671d13532014dd37ffd59363e9c138c4e54c61a5
+Subproject commit 5fbfd88c5885f1999f2c1dd4aecbcc2c5df47f20