.travis.yml: Remove pkg-config for brew doctor
.travis.yml: Remove pkg-config for brew doctor

rwhogg/brew,maxim-belkin/brew,hanxue/linuxbrew,Linuxbrew/brew,Linuxbrew/brew,rwhogg/brew,Linuxbrew/brew,hanxue/linuxbrew,rwhogg/brew,maxim-belkin/brew,maxim-belkin/brew,hanxue/linuxbrew,Linuxbrew/brew