slack-cli 1.16.4
slack-cli 1.16.4

Update slack-cli from 1.15.0 to 1.16.4

Closes #136048.

Signed-off-by: BrewTestBot <8a898ee6867e4f2028e63d2a6319b2224641c06c@users.noreply.github.com>

miccal/homebrew-cask,chrisfinazzo/homebrew-cask,andrewdisley/homebrew-cask,miccal/homebrew-cask,optikfluffel/homebrew-cask,optikfluffel/homebrew-cask,andrewdisley/homebrew-cask,andrewdisley/homebrew-cask,chrisfinazzo/homebrew-cask,miccal/homebrew-cask,optikfluffel/homebrew-cask,chrisfinazzo/homebrew-cask