[roll third_party/pigweed] pw_protobuf: Deprecate old encoder

Marks the old pw::protobuf::Encoder as deprecated. For the interim, use
pigweed's new pw::protobuf::StreamingEncoder. The
pw::protobuf::MemoryEncoder will be renamed to replace the original
Encoder.

Bugs: 384
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/46621

third_party/pigweed Rolled-Commits: b44d95e599b68c3..32988e0ba004ca4
Roller-URL: https://ci.chromium.org/b/8840531090570142160
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8840531090570142160
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Iac84372b02cb59805e2e8627e56782354aa749a8
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/54861
Reviewed-by: 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 b44d95e..32988e0 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit b44d95e599b68c30b8b342ce5e2587b1dba36ab3
+Subproject commit 32988e0ba004ca4ad344b9e6095385c2d9d152e3