pw_function: Fix fbl::Function link
pw_function: Fix fbl::Function link

Fuchsia deprecated and removed fbl::Function. This CL updates the
link to it to point at the last Fuchsia revision before it was removed.

Change-Id: Icf5dee93bf860faad29084ab648461682a565e64
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/95723
Reviewed-by: Armando Montanez <97ef6fdb231c129ac8827d9f0c4106bfbf57f74f@google.com>
Pigweed-Auto-Submit: RJ Ascani <4734195edb8e393f72741de86b813743e1460cb1@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