[roll third_party/pigweed] docs: Doxygenify pw::base64::EncodedSize()

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/149432

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 25d58ad86940055..c359686b4a32ba9
Roller-URL: https://ci.chromium.org/b/8779565194486127281
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I9827788ec232fab2031e8942c43b082db4bad305
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/149711
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 25d58ad..c359686 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 25d58ad86940055e9cee4871a12ca932276ef5ff
+Subproject commit c359686b4a32ba99d227ee4d3650119b0084b906