roll: pigweed pw_multibuf: Remove MultiBuf's Chunk iterator wrappers

Instead, use the iterators in MultiBufChunks directly. This avoids
having two different iterator types in one class.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/230893
Original-Revision: e31487f84caccbbfc986d8c6327c278ff1548c7d

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 6b20a021cf616e..e31487f84caccb
Roller-URL: https://ci.chromium.org/b/8736211408051995665
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I063273bce896e14242e73682e3f78c60a78668ee
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/quickstart/bazel/+/237085
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
diff --git a/MODULE.bazel b/MODULE.bazel
index ba90d62..665f72e 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -48,18 +48,18 @@
 git_override(
     module_name = "pigweed",
     # ROLL: Warning: this entry is automatically updated.
-    # ROLL: Last updated 2024-09-20.
-    # ROLL: By https://cr-buildbucket.appspot.com/build/8736234501767616705.
-    commit = "6b20a021cf616e20749c3eeb9cdbf8ebff12dcca",
+    # ROLL: Last updated 2024-09-21.
+    # ROLL: By https://cr-buildbucket.appspot.com/build/8736211408051995665.
+    commit = "e31487f84caccbbfc986d8c6327c278ff1548c7d",
     remote = "https://pigweed.googlesource.com/pigweed/pigweed",
 )
 
 git_override(
     module_name = "pw_toolchain",
     # ROLL: Warning: this entry is automatically updated.
-    # ROLL: Last updated 2024-09-20.
-    # ROLL: By https://cr-buildbucket.appspot.com/build/8736234501767616705.
-    commit = "6b20a021cf616e20749c3eeb9cdbf8ebff12dcca",
+    # ROLL: Last updated 2024-09-21.
+    # ROLL: By https://cr-buildbucket.appspot.com/build/8736211408051995665.
+    commit = "e31487f84caccbbfc986d8c6327c278ff1548c7d",
     remote = "https://pigweed.googlesource.com/pigweed/pigweed",
     strip_prefix = "pw_toolchain_bazel",
 )