[roll third_party/pigweed] pw_kvs: Remove unused fake flash partition

Remove fake_flash_small_partition that is no longer used.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/53740

third_party/pigweed Rolled-Commits: 60465a7872427ed..4b4767e080419da
Roller-URL: https://ci.chromium.org/b/8841164448678056928
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8841164448678056928
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Id502954debeb498ba44c219e15bfa3e44ecf1303
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/53801
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 60465a7..4b4767e 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 60465a7872427ed4fab9d0683ea1e52cededde7d
+Subproject commit 4b4767e080419da8b27093838c773c68c8a75c0b