Revert "[Travis] Workaround for https://github.com/travis-ci/travis-ci/issues/7031"

This reverts commit 51645020c6fd630ec83d5d66d05b13dd40d8d4a4.

.travis.yml

@@ -12,8 +12,6 @@ matrix:
     env: JOB=macOS
     os: osx
     osx_image: xcode8.2
-    before_install:
-      - xcrun simctl delete E40727B3-41FB-4D6E-B4CB-BFA87109EB12
   - script: docker run -v `pwd`:`pwd` -w `pwd` norionomura/sourcekit:302 swift test
     env: JOB=Linux-Swift3.0.2
     sudo: required