travis: Really delete the doc folder

Got two location to look at, be sure to delete them both.

Author: alexcrichton

.travis.yml

@@ -109,11 +109,12 @@ cache:
 
 before_deploy:
   - mkdir -p deploy/$TRAVIS_COMMIT
-  - rm -rf build/dist/doc
   - >
       if [ "$TRAVIS_OS_NAME" == "osx" ]; then
+          rm -rf build/dist/doc &&
           cp -r build/dist/* deploy/$TRAVIS_COMMIT;
       else
+          rm -rf obj/build/dist/doc &&
           cp -r obj/build/dist/* deploy/$TRAVIS_COMMIT;
       fi