pw_watch: Use os.fsdecode
pw_watch: Use os.fsdecode

Use os.fsdecode on filesystem paths, as a replacement for unicode_paths
from the watcher package.

Change-Id: Ie3059781516f5fd724df63d7c9bc2cde389476ed
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/27260
Pigweed-Auto-Submit: Wyatt Hepler <cca3bedb37979eacd157a9bceb473582df8aea1e@google.com>
Commit-Queue: Auto-Submit <14637eda5603879df170705285bf30f5996692f0@pigweed.google.com.iam.gserviceaccount.com>
Reviewed-by: Keir Mierle <69344103cc60b36d6e1fbdc31ce6504b2286c646@google.com>

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