circle.yml: Do not install curl. Use the host's
circle.yml: Do not install curl. Use the host's

test-bot removing openssl causes the brewed curl to fail.

LinuxbrewTestBot/homebrew-core,LinuxbrewTestBot/homebrew-core,maxim-belkin/homebrew-core,maxim-belkin/homebrew-core,Linuxbrew/homebrew-core,rwhogg/homebrew-core,rwhogg/homebrew-core,Linuxbrew/homebrew-core