Fix typo in circleci config

Author: pascalwengerter

.circleci/config.yml

@@ -63,7 +63,7 @@ jobs:
  bundle exec rspec --format progress \
  --out /tmp/test-results/rspec.xml \
  --format progress \
- -- {$TEST_FILES}
+ -- ${TEST_FILES}
 
  - run:
  name: Code Climate Test Coverage