fixes for grammar and wording

Library/Homebrew/build.rb

Library/Homebrew/cask/artifact/abstract_uninstall.rb

Library/Homebrew/cask/artifact/moved.rb

Library/Homebrew/cask/artifact/relocated.rb

Library/Homebrew/cask/artifact/symlinked.rb

Library/Homebrew/cask/cask_loader.rb

Library/Homebrew/cask/cmd/abstract_command.rb

Library/Homebrew/cask/cmd/internal_stanza.rb

Library/Homebrew/cask/download.rb

Library/Homebrew/cask/dsl.rb

Library/Homebrew/cask/dsl/caveats.rb

Library/Homebrew/cask/dsl/container.rb

Library/Homebrew/cask/dsl/depends_on.rb

Library/Homebrew/cask/installer.rb

Library/Homebrew/cask/metadata.rb

Library/Homebrew/cask/staged.rb

Library/Homebrew/caveats.rb

Library/Homebrew/cmd/fetch.rb

Library/Homebrew/cmd/install.rb

Library/Homebrew/cmd/link.rb