Removed rabbitmq fix from travis.yml

Upstream fix has been applied by Travis CI

Author: Cruz Monrreal II

.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
-  # import the new keys for rabbitmq (fix for https://github.com/ARMmbed/mbed-os/issues/8945)
-  - curl -s https://packagecloud.io/install/repositories/rabbitmq/rabbitmq-server/script.deb.sh | sudo bash
   # Loop until update succeeds (timeouts can occur)
   - travis_retry $(! sudo apt-get update 2>&1 |grep Failed)