travis: We don't use SDL_net anymore

.travis.yml

@@ -48,7 +48,7 @@ before_install:
 install:
     - if [ "$CXXSTD" == "1y" ]; then sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y; fi
     - travis_wait sudo apt-get update -qq
-    - travis_wait sudo apt-get install -qq libboost-filesystem-dev libboost-iostreams-dev libboost-random-dev libboost-program-options-dev libboost-regex-dev libboost-system-dev libboost-test-dev libboost-locale-dev libboost-thread-dev libcairo2-dev libfribidi-dev libpango1.0-dev libsdl2-image-dev libsdl2-mixer-dev libsdl2-net-dev libsdl2-ttf-dev libvorbis-dev gdb moreutils scons xvfb cmake
+    - travis_wait sudo apt-get install -qq libboost-filesystem-dev libboost-iostreams-dev libboost-random-dev libboost-program-options-dev libboost-regex-dev libboost-system-dev libboost-test-dev libboost-locale-dev libboost-thread-dev libcairo2-dev libfribidi-dev libpango1.0-dev libsdl2-image-dev libsdl2-mixer-dev libsdl2-ttf-dev libvorbis-dev gdb moreutils scons xvfb cmake
 
     - if [ "$CXXSTD" == "1y" ]; then
           sudo apt-get install -qq g++-5;