remove not needed anymore libffi fix

Author: GuillaumeGomez

.travis.yml

@@ -47,9 +47,6 @@ addons:
 before_install:
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update; fi
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install gtk+3 cairo atk; fi
-  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then
-    export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig:/opt/X11/lib/pkgconfig:/usr/local/opt/libffi/lib/pkgconfig;
-    fi
 script:
   - rustc --version
   - if [ "$TRAVIS_RUST_VERSION" == "stable" ] && [ "$GTK" == "3.14" ]; then