Reverting --precice_branch flag from travis file

Author: IshaanDesai

.travis.yml

@@ -34,7 +34,7 @@ matrix:
     env: PY=python3
     script:
     - curl -LO --retry 3 https://raw.githubusercontent.com/precice/systemtests/master/trigger_systemtests.py
-    - travis_wait 60 $PY trigger_systemtests.py --adapter fenics --precice_branch master --wait
+    - travis_wait 60 $PY trigger_systemtests.py --adapter fenics --wait
 
   - os: osx
     name: "Mock tests [OSx]"