docs: Fix public headers description
docs: Fix public headers description

Change-Id: Id5bf5a5406409a6f31d44506c54b0885d6c3dd22
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/108911
Reviewed-by: Alexei Frolov <a1b001416a8cf9aaea32a3411f8f3c0793ebc0b5@google.com>
Commit-Queue: Adam MacBeth <266b6a61ac7468691cb5a2ae06f5270d4a072e74@google.com>

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed