bug.yml: fix missing `label` property (#90232)
bug.yml: fix missing `label` property (#90232)

Submitting bug reports hasn't worked for a while because of the missing
`label`.

My editor complained about `labels` needing to be an array, so I've made
that one too. It was also complaining about the missing label property
for the checkboxes, so I guess it knows what it's talking about here.

See https://github.com/Homebrew/discussions/discussions/2526#discussioncomment-1731168
sjackman/homebrew-core,adam-moss/homebrew-core,stgraber/homebrew-core,chrisfinazzo/homebrew-core,makigumo/homebrew-core,adam-moss/homebrew-core,nandub/homebrew-core,uyjulian/homebrew-core,Homebrew/homebrew-core,cblecker/homebrew-core,sjackman/homebrew-core,mfikes/homebrew-core,makigumo/homebrew-core,lemzwerg/homebrew-core,filcab/homebrew-core,nandub/homebrew-core,chrisfinazzo/homebrew-core,mfikes/homebrew-core,Homebrew/homebrew-core,cblecker/homebrew-core,zyedidia/homebrew-core,nbari/homebrew-core,zyedidia/homebrew-core,uyjulian/homebrew-core,stgraber/homebrew-core,lemzwerg/homebrew-core,nbari/homebrew-core,filcab/homebrew-core