travis: mangodb key update not needed anymore

Author: 0xc0170

.travis.yml

@@ -30,8 +30,6 @@ before_install:
   # Setup ppa to make sure arm-none-eabi-gcc is correct version
   - sudo add-apt-repository -y ppa:team-gcc-arm-embedded/ppa
   - sudo add-apt-repository -y ppa:deadsnakes/ppa
-  # Fix for "The following signatures were invalid: KEYEXPIRED 1515625755" failed". See https://github.com/travis-ci/travis-ci/issues/9037
-  - sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 0C49F3730359A14518585931BC711F9BA15703C6
   # Loop until update succeeds (timeouts can occur)
   - travis_retry $(! sudo apt-get update 2>&1 |grep Failed)