[prebuilt] Update Black

Bug: 74877
Change-Id: I4b0feff0fc1b92597e6748cc27726331088b5c27
Reviewed-on: https://fuchsia-review.googlesource.com/c/infra/prebuilt/+/517702
Reviewed-by: Anthony Fandrianto <atyfto@google.com>
diff --git a/cipd.ensure b/cipd.ensure
index 6d287a1..7fe3de9 100644
--- a/cipd.ensure
+++ b/cipd.ensure
@@ -13,7 +13,7 @@
 
 # Black formatter
 # To update, see https://fuchsia.googlesource.com/infra/black/+/master/
-fuchsia/tools/black/${platform} version:19.10b0
+fuchsia/tools/black/${platform} version:20.8b1
 
 #
 # LUCI tools