fix(travis): adjust invalid make target

* `docs` is `docs-all` now. On travis, this should only build one API

Author: Byron

.travis.yml

@@ -1,6 +1,6 @@
 language: rust
 script:
-  - make docs cargo ARGS=test
+  - make docs-all cargo ARGS=test
 env:
   global:
     secure: Plj5DqAQX/4+KPM+nOAZ2sCbGIsoSrHo1YggfesQnU7paR734XO/4IayWnsNO/3q6bDi4GIcn56RUZAD3xBJJBNLia2CYIickIIYORRqLWbLdbzQaxBbD670ahtzEuUSFJTRKURPwFteAnsWYgNMNzwXOVNwLS5IUBqWTcS+N0g=