Travis CI: change to use the default email notification behavior
Travis CI: change to use the default email notification behavior

pierremoreau/SPIRV-Tools,KhronosGroup/SPIRV-Tools,LukasBanana/SPIRV-Tools,KhronosGroup/SPIRV-Tools,KhronosGroup/SPIRV-Tools,KhronosGroup/SPIRV-Tools,LukasBanana/SPIRV-Tools,KhronosGroup/SPIRV-Tools,antiagainst/SPIRV-Tools,dneto0/SPIRV-Tools,pierremoreau/SPIRV-Tools,antiagainst/SPIRV-Tools,pierremoreau/SPIRV-Tools,dneto0/SPIRV-Tools,dneto0/SPIRV-Tools,pierremoreau/SPIRV-Tools,pierremoreau/SPIRV-Tools,KhronosGroup/SPIRV-Tools,dneto0/SPIRV-Tools,antiagainst/SPIRV-Tools,antiagainst/SPIRV-Tools,LukasBanana/SPIRV-Tools,dneto0/SPIRV-Tools,dneto0/SPIRV-Tools,antiagainst/SPIRV-Tools,pierremoreau/SPIRV-Tools,dneto0/SPIRV-Tools,KhronosGroup/SPIRV-Tools,pierremoreau/SPIRV-Tools,dneto0/SPIRV-Tools,pierremoreau/SPIRV-Tools,KhronosGroup/SPIRV-Tools