[roll pigweed] pw_snapshot: Update software_version comments

Updates the inline documentation for the software_version field of the
snapshot Metadata proto message to clarify that the field is
intentionally not tokenizable.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/100800

https://pigweed.googlesource.com/pigweed/pigweed
pigweed Rolled-Commits: 74144e60b1b5664..a6ba963ad450193
Roller-URL: https://ci.chromium.org/b/8809805179483477905
Cq-Cl-Tag: roller-builder:pigweed-zephyr-roller
Cq-Cl-Tag: roller-bid:8809805179483477905
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I75ef0c9aea799bc9402fc3737c5e84182117d94d
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/zephyr-integration/+/100804
Bot-Commit: 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/pigweed b/pigweed
index 74144e6..a6ba963 160000
--- a/pigweed
+++ b/pigweed
@@ -1 +1 @@
-Subproject commit 74144e60b1b56648ccfb7136cbd1a1676ec9e80a
+Subproject commit a6ba963ad4501930243f0e6e20d81af3f09c477c