pw_file: Minor logging tweak
pw_file: Minor logging tweak

Silences NOT_FOUND error logging, as that isn't an error but instead is
an expected response.

Change-Id: Ia6faa65ed3a19503f53bf1299d7d717c275f12c3
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/71225
Pigweed-Auto-Submit: Armando Montanez <97ef6fdb231c129ac8827d9f0c4106bfbf57f74f@google.com>
Reviewed-by: Alexei Frolov <a1b001416a8cf9aaea32a3411f8f3c0793ebc0b5@google.com>
Commit-Queue: Auto-Submit <14637eda5603879df170705285bf30f5996692f0@pigweed.google.com.iam.gserviceaccount.com>

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