Travis : Remove `sudo: false`
Travis : Remove `sudo: false`

According to the [Travis blog](https://blog.travis-ci.com/2018-10-04-combining-linux-infrastructures?utm_source=changelog&utm_medium=web&utm_campaign=single_linux_stage_1) this is being taken away from us soon anyway.

boberfly/gaffer,ImageEngine/gaffer,GafferHQ/gaffer,GafferHQ/gaffer,andrewkaufman/gaffer,ImageEngine/gaffer,boberfly/gaffer,ImageEngine/gaffer,andrewkaufman/gaffer,GafferHQ/gaffer,hradec/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer,boberfly/gaffer,johnhaddon/gaffer,boberfly/gaffer,GafferHQ/gaffer,appleseedhq/gaffer,hradec/gaffer,appleseedhq/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer,johnhaddon/gaffer,appleseedhq/gaffer,lucienfostier/gaffer,GafferHQ/gaffer,andrewkaufman/gaffer,johnhaddon/gaffer,appleseedhq/gaffer,hradec/gaffer,lucienfostier/gaffer,hradec/gaffer,lucienfostier/gaffer,hradec/gaffer,lucienfostier/gaffer,ImageEngine/gaffer