[roll third_party/pigweed] docker: Copyedit the existing doc

Adding section headings makes the doc easier to scan. "Docker"
should be capitalized when referring to the general product. The
call-to-action was updated to point people to the issue tracker
rather than sending an email.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/151057

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: b5704b74f2b3280..1078532e5d21477
Roller-URL: https://ci.chromium.org/b/8778738451742192273
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ia415395aa6fb9389a65bbdc067adf013469409dd
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/151158
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index b5704b7..1078532 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit b5704b74f2b328063aa38914e6ddfdcc643653c0
+Subproject commit 1078532e5d21477c13c3b75e74a601edf1a6527d