[roll third_party/pigweed] pw_web: Fix invisible jump button

Changelist:
- Adds back removed styles for jump-to-bottom button
- Improves CSS grid performance when updating width values

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/175330

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 913f56cfd0ae11a..a96389142d68f63
Roller-URL: https://ci.chromium.org/b/8767495384135208641
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ibabd0758593374d9a5ae930517e02b2c01c49060
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/175537
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 913f56c..a963891 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 913f56cfd0ae11ad1f658a86cb7aa475b569fd2f
+Subproject commit a96389142d68f634c8645b186d93573b391e3fff