pw_software_update: Disable spurious Pylint error
pw_software_update: Disable spurious Pylint error

Followup to
https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/70301.
Removes another spurious pylint error.

Bug: 572
Change-Id: I44b8fad86baca384319740a352a0e0f75446a628
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/70840
Reviewed-by: Wyatt Hepler <cca3bedb37979eacd157a9bceb473582df8aea1e@google.com>
Commit-Queue: Ted Pudlik <c7372cc3e451acc046049fca9e050bcb2a4a3d11@google.com>

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