roll: third_party/pigweed pw_containers: Add std::variant support to pw::Hash

This change enables pw::Hash to correctly hash std::variant types. It
does this by mixing the variant's index with the hash of the currently
active alternative, which reduces hash collisions.

Original-Bug: 502843131
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/398252
Original-Revision: 261701bcf5ecdbd804544bc2b52be53481bdb959

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 32c6eae34ecae6..261701bcf5ecdb
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8683675947064696497
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I93ac0d18867392b68da8c4cb4b14457c79e8628b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/402215
diff --git a/third_party/pigweed b/third_party/pigweed
index 32c6eae..261701b 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 32c6eae34ecae66863dcb1eb32625825c971872d
+Subproject commit 261701bcf5ecdbd804544bc2b52be53481bdb959