[roll third_party/pigweed] docs/style_guide: revert stance on non-type template args

Reverts our stance on non-type template argument style to be
consistent with the naming standard applied to other varibles whose
value is fixed for the duration of the program, namely kCamelCase.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/39660

third_party/pigweed Rolled-Commits: f705151b650215b..ad2f3c35b1a8af0
Roller-URL: https://ci.chromium.org/b/8851209755739301104
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8851209755739301104
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I15bea9315198e38ef8286c41ba903c1e21a4bfac
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/39681
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 f705151..ad2f3c3 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit f705151b650215b6896b6764073273b82d49d10c
+Subproject commit ad2f3c35b1a8af005e3e0637efb1664b8d109ae9