Remove unneccessary 'bundle exec'
Remove unneccessary 'bundle exec'

This was interfering with the 'bundle install' invocation in the script,
and is not needed for the script to find the necessary gems.

Signed-off-by: Anna Thornton <0e9b4a17e1cf85a71a11118ecdbc866e5f8ffc65@pivotal.io>

cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci