Revert "added libyaml-perl to list of packages for Linux"

This reverts commit 1e842e24abfadaa0cadbd82ea89fe3170ddb3193.
diff --git a/.travis.yml b/.travis.yml
index ae2734a..ae9d06e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -77,7 +77,6 @@
       - libsmi2-dev
       - libcap-ng-dev
       - libpcap-dev
-      - libyaml-perl
 
 git:
   quiet: true
@@ -92,7 +91,7 @@
   - if [ "$TRAVIS_OS_NAME" = linux ]; then sudo update-ca-certificates; fi
 
 install:
-   - if [ "$TRAVIS_OS_NAME" = osx ]; then brew install libsmi cpanminus | grep -v '%'; cpanm --local-lib=~/perl5 local::lib && eval $(perl -I ~/perl5/lib/perl5/ -Mlocal::lib); cpanm YAML; fi
+  - if [ "$TRAVIS_OS_NAME" = osx ]; then brew install libsmi | grep -v '%'; fi
 
 before_script:
   - if [ "$BUILD_LIBPCAP" = yes ]; then (cd .. && echo '$ git clone [...] libpcap.git' && git clone --depth 3 --branch=master --quiet git://github.com/the-tcpdump-group/libpcap.git && cd libpcap && ./configure "--${REMOTE}-remote" --prefix=/tmp && make && make install); fi