[roll third_party/pigweed] docs: Mention that Windows flow needs admin rights

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/202030

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 849d99bd97a5613..517696e29810c51
Roller-URL: https://ci.chromium.org/b/8751533295145349905
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I3eb2e2d3745f47201f8cf326ce97f71e71f42232
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/202013
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 849d99b..517696e 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 849d99bd97a561308a17e2f7f29c9ab46ce8acd2
+Subproject commit 517696e29810c51426a1e6f3438ad7df2580bc74