build: remove travis_wait

Now the travis CI build time is fast enough to not cause build timeout.

Author: tesuji

.travis.yml

@@ -126,7 +126,7 @@ script:
     if [[ -n ${INTEGRATION} ]]; then
       ./ci/integration-tests.sh && sleep 5
     else
-      travis_wait 30 ./ci/base-tests.sh && sleep 5
+      ./ci/base-tests.sh && sleep 5
     fi
 
 after_success: