Bump github.com/slack-go/slack from 0.14.0 to 0.15.0#139

dependabot[bot] wants to merge 1 commit intomainmathew-fleisch/bashbot:mainfrom

dependabot/go_modules/github.com/slack-go/slack-0.15.0mathew-fleisch/bashbot:dependabot/go_modules/github.com/slack-go/slack-0.15.0Copy head branch name to clipboard