Update .travis.yml

Fix file not exist error when deploying

.travis.yml

@@ -12,7 +12,7 @@ script:
   - tar -czf result.tar.gz results
 
 before_deploy:
-  - rm .travis.yml .gitignore Gemfile Gemfile.lock extract_contents_csv.rb island_with_administrative_area.csv
+  - rm -f .travis.yml .gitignore Gemfile Gemfile.lock extract_contents_csv.rb island_with_administrative_area.csv
 
 deploy:
   - provider: releases